Merge pull request mozilla#342 from mozilla/greenkeeper-grunt-eslint-19.0.0

Update grunt-eslint to version 19.0.0 🚀

Author: kumar303

package.json

@@ -79,7 +79,7 @@
     "grunt-contrib-copy": "1.0.0",
     "grunt-contrib-watch": "1.0.0",
     "grunt-coveralls": "1.0.1",
-    "grunt-eslint": "18.1.0",
+    "grunt-eslint": "19.0.0",
     "grunt-flowbin": "0.0.5",
     "grunt-mocha-test": "0.12.7",
     "grunt-newer": "1.2.0",