chore(package): update mocha to version 5.2.0

Closes #255

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
   },
   "devDependencies": {
     "eslint": "^3.12.0",
-    "mocha": "^3.2.0",
+    "mocha": "^5.2.0",
     "nock": "^9.0.2"
   },
   "main": "./lib/twitter"