diff --git a/package.json b/package.json
index 7e5b548..78c2074 100644
--- a/package.json
+++ b/package.json
@@ -92,7 +92,7 @@
     "eslint-plugin-flowtype": "^2.30.0",
     "eslint-watch": "^3.0.0",
     "flow-bin": "^0.89.0",
-    "flow-copy-source": "^1.2.1",
+    "flow-copy-source": "^2.0.0",
     "flow-watch": "^1.1.0",
     "husky": "^0.14.3",
     "istanbul": "^0.4.5",
diff --git a/yarn.lock b/yarn.lock
index d10f68e..7157a49 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1493,6 +1493,10 @@ camelcase@^4.0.0, camelcase@^4.1.0:
   version "4.1.0"
   resolved "https://registry.npmjs.org/camelcase/-/camelcase-4.1.0.tgz#d545635be1e33c542649c69173e5de6acfae34dd"
 
+camelcase@^5.0.0:
+  version "5.0.0"
+  resolved "https://registry.yarnpkg.com/camelcase/-/camelcase-5.0.0.tgz#03295527d58bd3cd4aa75363f35b2e8d97be2f42"
+
 caniuse-lite@^1.0.30000792:
   version "1.0.30000792"
   resolved "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30000792.tgz#d0cea981f8118f3961471afbb43c9a1e5bbf0332"
@@ -1560,7 +1564,7 @@ check-error@^1.0.1:
   version "1.0.2"
   resolved "https://registry.npmjs.org/check-error/-/check-error-1.0.2.tgz#574d312edd88bb5dd8912e9286dd6c0aed4aac82"
 
-chokidar@^1.4.3, chokidar@^1.6.1, chokidar@^1.7.0:
+chokidar@^1.4.3, chokidar@^1.6.1:
   version "1.7.0"
   resolved "https://registry.npmjs.org/chokidar/-/chokidar-1.7.0.tgz#798e689778151c8076b4b360e5edd28cda2bb468"
   dependencies:
@@ -1641,14 +1645,6 @@ cliui@^2.1.0:
     right-align "^0.1.1"
     wordwrap "0.0.2"
 
-cliui@^3.2.0:
-  version "3.2.0"
-  resolved "https://registry.npmjs.org/cliui/-/cliui-3.2.0.tgz#120601537a916d29940f934da3b48d585a39213d"
-  dependencies:
-    string-width "^1.0.1"
-    strip-ansi "^3.0.1"
-    wrap-ansi "^2.0.0"
-
 cliui@^4.0.0:
   version "4.0.0"
   resolved "https://registry.npmjs.org/cliui/-/cliui-4.0.0.tgz#743d4650e05f36d1ed2575b59638d87322bfbbcc"
@@ -1968,7 +1964,7 @@ debug@^2.2.0, debug@^2.3.3, debug@^2.6.8:
   dependencies:
     ms "2.0.0"
 
-decamelize@^1.0.0, decamelize@^1.1.1, decamelize@^1.1.2:
+decamelize@^1.0.0, decamelize@^1.1.1, decamelize@^1.1.2, decamelize@^1.2.0:
   version "1.2.0"
   resolved "https://registry.npmjs.org/decamelize/-/decamelize-1.2.0.tgz#f6534d15148269b20352e7bee26f501f9a191290"
 
@@ -2527,6 +2523,12 @@ find-up@^2.0.0, find-up@^2.1.0:
   dependencies:
     locate-path "^2.0.0"
 
+find-up@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/find-up/-/find-up-3.0.0.tgz#49169f1d7993430646da61ecc5ae355c21c97b73"
+  dependencies:
+    locate-path "^3.0.0"
+
 findup@0.1.5:
   version "0.1.5"
   resolved "https://registry.npmjs.org/findup/-/findup-0.1.5.tgz#8ad929a3393bac627957a7e5de4623b06b0e2ceb"
@@ -2547,15 +2549,15 @@ flow-bin@^0.89.0:
   version "0.89.0"
   resolved "https://registry.yarnpkg.com/flow-bin/-/flow-bin-0.89.0.tgz#6bd29c2af7e0f429797f820662f33749105c32fa"
 
-flow-copy-source@^1.2.1:
-  version "1.2.1"
-  resolved "https://registry.npmjs.org/flow-copy-source/-/flow-copy-source-1.2.1.tgz#705c2fa8fb29a281118e1c4b66218dec24b745ec"
+flow-copy-source@^2.0.0:
+  version "2.0.2"
+  resolved "https://registry.yarnpkg.com/flow-copy-source/-/flow-copy-source-2.0.2.tgz#096e579a9bb63a38afc5d4dd68ac847a5be27594"
   dependencies:
-    chokidar "^1.7.0"
-    fs-extra "^3.0.1"
+    chokidar "^2.0.0"
+    fs-extra "^7.0.0"
     glob "^7.0.0"
     kefir "^3.7.3"
-    yargs "^8.0.2"
+    yargs "^12.0.1"
 
 flow-watch@^1.1.0:
   version "1.1.1"
@@ -2627,17 +2629,17 @@ fs-exists-sync@^0.1.0:
   version "0.1.0"
   resolved "https://registry.npmjs.org/fs-exists-sync/-/fs-exists-sync-0.1.0.tgz#982d6893af918e72d08dec9e8673ff2b5a8d6add"
 
-fs-extra@^3.0.1:
-  version "3.0.1"
-  resolved "https://registry.npmjs.org/fs-extra/-/fs-extra-3.0.1.tgz#3794f378c58b342ea7dbbb23095109c4b3b62291"
+fs-extra@^5.0.0:
+  version "5.0.0"
+  resolved "https://registry.npmjs.org/fs-extra/-/fs-extra-5.0.0.tgz#414d0110cdd06705734d055652c5411260c31abd"
   dependencies:
     graceful-fs "^4.1.2"
-    jsonfile "^3.0.0"
+    jsonfile "^4.0.0"
     universalify "^0.1.0"
 
-fs-extra@^5.0.0:
-  version "5.0.0"
-  resolved "https://registry.npmjs.org/fs-extra/-/fs-extra-5.0.0.tgz#414d0110cdd06705734d055652c5411260c31abd"
+fs-extra@^7.0.0:
+  version "7.0.1"
+  resolved "https://registry.yarnpkg.com/fs-extra/-/fs-extra-7.0.1.tgz#4f189c44aa123b895f722804f55ea23eadc348e9"
   dependencies:
     graceful-fs "^4.1.2"
     jsonfile "^4.0.0"
@@ -3191,6 +3193,10 @@ invert-kv@^1.0.0:
   version "1.0.0"
   resolved "https://registry.npmjs.org/invert-kv/-/invert-kv-1.0.0.tgz#104a8e4aaca6d3d8cd157a8ef8bfab2d7a3ffdb6"
 
+invert-kv@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/invert-kv/-/invert-kv-2.0.0.tgz#7393f5afa59ec9ff5f67a27620d11c226e3eec02"
+
 is-absolute@^0.2.5:
   version "0.2.6"
   resolved "https://registry.npmjs.org/is-absolute/-/is-absolute-0.2.6.tgz#20de69f3db942ef2d87b9c2da36f172235b1b5eb"
@@ -3641,12 +3647,6 @@ json5@^0.5.1:
   version "0.5.1"
   resolved "https://registry.npmjs.org/json5/-/json5-0.5.1.tgz#1eade7acc012034ad84e2396767ead9fa5495821"
 
-jsonfile@^3.0.0:
-  version "3.0.1"
-  resolved "https://registry.npmjs.org/jsonfile/-/jsonfile-3.0.1.tgz#a5ecc6f65f53f662c4415c7675a0331d0992ec66"
-  optionalDependencies:
-    graceful-fs "^4.1.6"
-
 jsonfile@^4.0.0:
   version "4.0.0"
   resolved "https://registry.npmjs.org/jsonfile/-/jsonfile-4.0.0.tgz#8771aae0799b64076b76640fca058f9c10e33ecb"
@@ -3732,6 +3732,12 @@ lcid@^1.0.0:
   dependencies:
     invert-kv "^1.0.0"
 
+lcid@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/lcid/-/lcid-2.0.0.tgz#6ef5d2df60e52f82eb228a4c373e8d1f397253cf"
+  dependencies:
+    invert-kv "^2.0.0"
+
 lcov-parse@^0.0.10:
   version "0.0.10"
   resolved "https://registry.yarnpkg.com/lcov-parse/-/lcov-parse-0.0.10.tgz#1b0b8ff9ac9c7889250582b70b71315d9da6d9a3"
@@ -3753,15 +3759,6 @@ load-json-file@^1.0.0:
     pinkie-promise "^2.0.0"
     strip-bom "^2.0.0"
 
-load-json-file@^2.0.0:
-  version "2.0.0"
-  resolved "https://registry.npmjs.org/load-json-file/-/load-json-file-2.0.0.tgz#7947e42149af80d696cbf797bcaabcfe1fe29ca8"
-  dependencies:
-    graceful-fs "^4.1.2"
-    parse-json "^2.2.0"
-    pify "^2.0.0"
-    strip-bom "^3.0.0"
-
 load-json-file@^4.0.0:
   version "4.0.0"
   resolved "https://registry.npmjs.org/load-json-file/-/load-json-file-4.0.0.tgz#2f5f45ab91e33216234fd53adab668eb4ec0993b"
@@ -3778,6 +3775,13 @@ locate-path@^2.0.0:
     p-locate "^2.0.0"
     path-exists "^3.0.0"
 
+locate-path@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/locate-path/-/locate-path-3.0.0.tgz#dbec3b3ab759758071b58fe59fc41871af21400e"
+  dependencies:
+    p-locate "^3.0.0"
+    path-exists "^3.0.0"
+
 lodash-es@^4.2.1:
   version "4.17.4"
   resolved "https://registry.npmjs.org/lodash-es/-/lodash-es-4.17.4.tgz#dcc1d7552e150a0640073ba9cb31d70f032950e7"
@@ -3904,6 +3908,12 @@ make-dir@^1.0.0:
   dependencies:
     pify "^3.0.0"
 
+map-age-cleaner@^0.1.1:
+  version "0.1.3"
+  resolved "https://registry.yarnpkg.com/map-age-cleaner/-/map-age-cleaner-0.1.3.tgz#7d583a7306434c055fe474b0f45078e6e1b4b92a"
+  dependencies:
+    p-defer "^1.0.0"
+
 map-cache@^0.2.2:
   version "0.2.2"
   resolved "https://registry.npmjs.org/map-cache/-/map-cache-0.2.2.tgz#c32abd0bd6525d9b051645bb4f26ac5dc98a0dbf"
@@ -3966,6 +3976,14 @@ mem@^1.1.0:
   dependencies:
     mimic-fn "^1.0.0"
 
+mem@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/mem/-/mem-4.0.0.tgz#6437690d9471678f6cc83659c00cbafcd6b0cdaf"
+  dependencies:
+    map-age-cleaner "^0.1.1"
+    mimic-fn "^1.0.0"
+    p-is-promise "^1.1.0"
+
 meow@3.7.0, meow@^3.3.0:
   version "3.7.0"
   resolved "https://registry.npmjs.org/meow/-/meow-3.7.0.tgz#72cb668b425228290abbfa856892587308a801fb"
@@ -4396,6 +4414,14 @@ os-locale@^2.0.0:
     lcid "^1.0.0"
     mem "^1.1.0"
 
+os-locale@^3.0.0:
+  version "3.0.1"
+  resolved "https://registry.yarnpkg.com/os-locale/-/os-locale-3.0.1.tgz#3b014fbf01d87f60a1e5348d80fe870dc82c4620"
+  dependencies:
+    execa "^0.10.0"
+    lcid "^2.0.0"
+    mem "^4.0.0"
+
 os-tmpdir@^1.0.0, os-tmpdir@^1.0.1, os-tmpdir@~1.0.2:
   version "1.0.2"
   resolved "https://registry.npmjs.org/os-tmpdir/-/os-tmpdir-1.0.2.tgz#bbe67406c79aa85c5cfec766fe5734555dfa1274"
@@ -4419,6 +4445,10 @@ p-cancelable@^0.3.0:
   version "0.3.0"
   resolved "https://registry.npmjs.org/p-cancelable/-/p-cancelable-0.3.0.tgz#b9e123800bcebb7ac13a479be195b507b98d30fa"
 
+p-defer@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/p-defer/-/p-defer-1.0.0.tgz#9f6eb182f6c9aa8cd743004a7d4f96b196b0fb0c"
+
 p-finally@^1.0.0:
   version "1.0.0"
   resolved "https://registry.npmjs.org/p-finally/-/p-finally-1.0.0.tgz#3fbcfb15b899a44123b34b6dcc18b724336a2cae"
@@ -4433,12 +4463,24 @@ p-limit@^1.1.0:
   dependencies:
     p-try "^1.0.0"
 
+p-limit@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/p-limit/-/p-limit-2.0.0.tgz#e624ed54ee8c460a778b3c9f3670496ff8a57aec"
+  dependencies:
+    p-try "^2.0.0"
+
 p-locate@^2.0.0:
   version "2.0.0"
   resolved "https://registry.npmjs.org/p-locate/-/p-locate-2.0.0.tgz#20a0103b222a70c8fd39cc2e580680f3dde5ec43"
   dependencies:
     p-limit "^1.1.0"
 
+p-locate@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/p-locate/-/p-locate-3.0.0.tgz#322d69a05c0264b25997d9f40cd8a891ab0064a4"
+  dependencies:
+    p-limit "^2.0.0"
+
 p-reduce@^1.0.0:
   version "1.0.0"
   resolved "https://registry.npmjs.org/p-reduce/-/p-reduce-1.0.0.tgz#18c2b0dd936a4690a529f8231f58a0fdb6a47dfa"
@@ -4459,6 +4501,10 @@ p-try@^1.0.0:
   version "1.0.0"
   resolved "https://registry.npmjs.org/p-try/-/p-try-1.0.0.tgz#cbc79cdbaf8fd4228e13f621f2b1a237c1b207b3"
 
+p-try@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/p-try/-/p-try-2.0.0.tgz#85080bb87c64688fa47996fe8f7dfbe8211760b1"
+
 package-json@^4.0.0:
   version "4.0.1"
   resolved "https://registry.npmjs.org/package-json/-/package-json-4.0.1.tgz#8869a0401253661c4c4ca3da6c2121ed555f5eed"
@@ -4553,12 +4599,6 @@ path-type@^1.0.0:
     pify "^2.0.0"
     pinkie-promise "^2.0.0"
 
-path-type@^2.0.0:
-  version "2.0.0"
-  resolved "https://registry.npmjs.org/path-type/-/path-type-2.0.0.tgz#f012ccb8415b7096fc2daa1054c3d72389594c73"
-  dependencies:
-    pify "^2.0.0"
-
 path-type@^3.0.0:
   version "3.0.0"
   resolved "https://registry.npmjs.org/path-type/-/path-type-3.0.0.tgz#cef31dc8e0a1a3bb0d105c0cd97cf3bf47f4e36f"
@@ -4710,13 +4750,6 @@ read-pkg-up@^1.0.1:
     find-up "^1.0.0"
     read-pkg "^1.0.0"
 
-read-pkg-up@^2.0.0:
-  version "2.0.0"
-  resolved "https://registry.npmjs.org/read-pkg-up/-/read-pkg-up-2.0.0.tgz#6b72a8048984e0c41e79510fd5e9fa99b3b549be"
-  dependencies:
-    find-up "^2.0.0"
-    read-pkg "^2.0.0"
-
 read-pkg-up@^3.0.0:
   version "3.0.0"
   resolved "https://registry.npmjs.org/read-pkg-up/-/read-pkg-up-3.0.0.tgz#3ed496685dba0f8fe118d0691dc51f4a1ff96f07"
@@ -4732,14 +4765,6 @@ read-pkg@^1.0.0:
     normalize-package-data "^2.3.2"
     path-type "^1.0.0"
 
-read-pkg@^2.0.0:
-  version "2.0.0"
-  resolved "https://registry.npmjs.org/read-pkg/-/read-pkg-2.0.0.tgz#8ef1c0623c6a6db0dc6713c4bfac46332b2368f8"
-  dependencies:
-    load-json-file "^2.0.0"
-    normalize-package-data "^2.3.2"
-    path-type "^2.0.0"
-
 read-pkg@^3.0.0:
   version "3.0.0"
   resolved "https://registry.npmjs.org/read-pkg/-/read-pkg-3.0.0.tgz#9cbc686978fee65d16c00e2b19c237fcf6e38389"
@@ -5945,15 +5970,20 @@ y18n@^3.2.1:
   version "3.2.1"
   resolved "https://registry.npmjs.org/y18n/-/y18n-3.2.1.tgz#6d15fba884c08679c0d77e88e7759e811e07fa41"
 
+"y18n@^3.2.1 || ^4.0.0":
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/y18n/-/y18n-4.0.0.tgz#95ef94f85ecc81d007c264e190a120f0a3c8566b"
+
 yallist@^2.1.2:
   version "2.1.2"
   resolved "https://registry.npmjs.org/yallist/-/yallist-2.1.2.tgz#1c11f9218f076089a47dd512f93c6699a6a81d52"
 
-yargs-parser@^7.0.0:
-  version "7.0.0"
-  resolved "https://registry.npmjs.org/yargs-parser/-/yargs-parser-7.0.0.tgz#8d0ac42f16ea55debd332caf4c4038b3e3f5dfd9"
+yargs-parser@^11.1.1:
+  version "11.1.1"
+  resolved "https://registry.yarnpkg.com/yargs-parser/-/yargs-parser-11.1.1.tgz#879a0865973bca9f6bab5cbdf3b1c67ec7d3bcf4"
   dependencies:
-    camelcase "^4.1.0"
+    camelcase "^5.0.0"
+    decamelize "^1.2.0"
 
 yargs-parser@^8.0.0, yargs-parser@^8.1.0:
   version "8.1.0"
@@ -6001,23 +6031,22 @@ yargs@^11.0.0:
     y18n "^3.2.1"
     yargs-parser "^9.0.2"
 
-yargs@^8.0.2:
-  version "8.0.2"
-  resolved "https://registry.npmjs.org/yargs/-/yargs-8.0.2.tgz#6299a9055b1cefc969ff7e79c1d918dceb22c360"
+yargs@^12.0.1:
+  version "12.0.5"
+  resolved "https://registry.yarnpkg.com/yargs/-/yargs-12.0.5.tgz#05f5997b609647b64f66b81e3b4b10a368e7ad13"
   dependencies:
-    camelcase "^4.1.0"
-    cliui "^3.2.0"
-    decamelize "^1.1.1"
+    cliui "^4.0.0"
+    decamelize "^1.2.0"
+    find-up "^3.0.0"
     get-caller-file "^1.0.1"
-    os-locale "^2.0.0"
-    read-pkg-up "^2.0.0"
+    os-locale "^3.0.0"
     require-directory "^2.1.1"
     require-main-filename "^1.0.1"
     set-blocking "^2.0.0"
     string-width "^2.0.0"
     which-module "^2.0.0"
-    y18n "^3.2.1"
-    yargs-parser "^7.0.0"
+    y18n "^3.2.1 || ^4.0.0"
+    yargs-parser "^11.1.1"
 
 yargs@~3.10.0:
   version "3.10.0"