chore(package): update eslint to version 5.12.1

Closes #12

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
     "browserify": "^14.0.0",
     "chai": "^4.0.0",
     "coveralls": "^2.11.6",
-    "eslint": "^3.0.0",
+    "eslint": "^5.12.1",
     "istanbul": "^0.4.1",
     "mocha": "^3.0.2"
   }