chore(deps): update dependency license-checker to v20 (#15)

Author: renovate[bot]

package.json

@@ -79,7 +79,7 @@
     "dont-crack": "1.2.1",
     "git-issues": "1.3.1",
     "github-post-release": "1.13.1",
-    "license-checker": "15.0.0",
+    "license-checker": "20.2.0",
     "mocha": "5.2.0",
     "nsp": "2.8.1",
     "pre-git": "3.17.1",