chore(package): update gulp-eslint to version 6.0.0

Closes #115

Author: greenkeeper[bot]

package.json

@@ -56,7 +56,7 @@
     "estraverse-fb": "^1.3.1",
     "gulp": "^3.9.1",
     "gulp-babel": "^7.0.0",
-    "gulp-eslint": "^4.0.0",
+    "gulp-eslint": "^6.0.0",
     "mocha": "^3.4.2",
     "pg-native": "^2.0.1"
   }