chore(package): update mocha to version 6.2.1

Closes #78

Author: greenkeeper[bot]

package.json

@@ -60,7 +60,7 @@
     "cross-env": "^5.2.0",
     "eslint": "^6.0.0",
     "istanbul": "^0.4.5",
-    "mocha": "^5.2.0",
+    "mocha": "^6.2.1",
     "nodemon": "^1.17.5",
     "nyc": "^13.1.0",
     "request": "^2.87.0",