chore(package): update eslint-plugin-mocha to version 6.2.1

Closes #15

Author: greenkeeper[bot]

package.json

@@ -6,7 +6,7 @@
   "devDependencies": {
     "del": "^3.0.0",
     "eslint": "^5.0.0",
-    "eslint-plugin-mocha": "^5.0.0",
+    "eslint-plugin-mocha": "^6.2.1",
     "gulp": "^3.9.0",
     "gulp-eslint": "^5.0.0",
     "husky": "^1.0.0",