chore(package): update mocha to version 6.1.0

Closes #61

Author: greenkeeper[bot]

package.json

@@ -44,6 +44,6 @@
     "eslint": "^3.10.2",
     "eslint-config-airbnb-base": "^11.1.2",
     "eslint-plugin-import": "^2.2.0",
-    "mocha": "^3.2.0"
+    "mocha": "^6.1.0"
   }
 }