chore(package): update sinon to version 9.0.1

Closes #243

Author: greenkeeper[bot]

Diff for: package.json

@@ -104,7 +104,7 @@
     "nodemon": "^1.12.1",
     "npm-run-all": "^4.1.1",
     "selenium-standalone": "^6.13.0",
-    "sinon": "^6.0.0",
+    "sinon": "^9.0.1",
     "supertest": "^3.0.0"
   },
   "ava": {