chore(package): update mocha to version 6.1.3

Closes #56

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
     "grunt-contrib-coffee": "^2.0.0",
     "grunt-mocha-test": "^0.13.2",
     "grunt-shell-spawn": "^0.3.1",
-    "mocha": "^5.0.0",
+    "mocha": "^6.1.3",
     "mqtt": "^2.7.1"
   },
   "keywords": [],