chore(package): update mocha to version 6.2.2

Closes #81

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
     "eslint": "^4.6.0",
     "eslint-config-airbnb-base": "^12.0.0",
     "eslint-plugin-import": "^2.7.0",
-    "mocha": "^5.0.0"
+    "mocha": "^6.2.2"
   },
   "scripts": {
     "test": "npm run test:lint && npm run test:unit && npm run test:integration",