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

Closes #36

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
 		"chai-as-promised": "7.1.1",
 		"express": "latest",
 		"gulp": "3.9.1",
-		"gulp-eslint": "4.0.2",
+		"gulp-eslint": "6.0.0",
 		"gulp-mocha": "5.0.0",
 		"mocha": "5.1.0",
 		"run-sequence": "2.2.1"