chore(package): update mocha to version 6.2.0

Closes #20

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
   "devDependencies": {
     "chai": "^4.1.0",
     "coffee-script": "^1.10.0",
-    "mocha": "^5.0.0",
+    "mocha": "^6.2.0",
     "amqplib": "^0.5.1",
     "mqtt": "^2.13.0",
     "msgflo": "^0.11.0"