chore(package): update eslint to version 4.18.0

Closes #40

Author: greenkeeper[bot]

package.json

@@ -46,7 +46,7 @@
     "chai": "^4.0.2",
     "cli-character-set": "^0.1.0",
     "coveralls": "^2.11.6",
-    "eslint": "^3.0.0",
+    "eslint": "^4.18.0",
     "glob": "^7.0.0",
     "istanbul": "^0.4.1",
     "mocha": "^3.0.2",