chore(package): update eslint to version 6.3.0

Closes #19

Author: greenkeeper[bot]

package.json

@@ -11,7 +11,7 @@
   },
   "devDependencies": {
     "@neogeek/eslint-config-standards": "^1.15.0",
-    "eslint": "^4.5.0",
+    "eslint": "^6.3.0",
     "grunt": "^1.0.1",
     "grunt-mkdir": "^1.0.0",
     "grunt-mocha-test": "^0.13.2",