chore(package): update eslint to version 4.19.0

Closes #19

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
     "browserify": "^14.3.0",
     "chai": "^4.0.1",
     "coveralls": "^2.11.9",
-    "eslint": "^3.0.0",
+    "eslint": "^4.19.0",
     "istanbul": "^0.4.3",
     "mocha": "^3.0.2"
   }