chore(package): update mocha to version 6.1.0

Closes #458

Author: greenkeeper[bot]

package.json

@@ -50,7 +50,7 @@
     "enzyme": "^3.3.0",
     "enzyme-adapter-react-16": "^1.1.1",
     "jsdom": "11.9.0",
-    "mocha": "^5.1.1",
+    "mocha": "^6.1.0",
     "node-sass": "^4.8.3",
     "npm-run-all": "^4.1.2",
     "nyc": "^11.7.1",