chore(package): update eslint to version 6.7.2

Closes #54

Author: greenkeeper[bot]

package.json

@@ -32,7 +32,7 @@
     "chai": "~4.1.0",
     "chalk": "~2.4.0",
     "coveralls": "~3.0.0",
-    "eslint": "~4.19.0",
+    "eslint": "~6.7.2",
     "istanbul": "~0.4.5",
     "minimist": "~1.2.0",
     "mocha": "~6.2.2",