chore(package): update eslint to version 6.3.0

Closes #50

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
     "chai": "^4.1.2",
     "coveralls": "^3.0.2",
     "cross-env": "^5.2.0",
-    "eslint": "^5.2.0",
+    "eslint": "^6.3.0",
     "hoek": "^6.0.0",
     "jsdom": "^14.0.0",
     "jsdom-global": "^3.0.2",