chore(package): update mocha to version 7.1.0

Closes #31

Author: greenkeeper[bot]

package.json

@@ -60,7 +60,7 @@
     "firebase-tools": "^4.1.2",
     "husky": "^2.0.0",
     "istanbul": "^0.4.5",
-    "mocha": "^6.0.0",
+    "mocha": "^7.1.0",
     "rimraf": "^2.6.2",
     "semantic-release": "^15.9.9",
     "travis-deploy-once": "^5.0.2"