chore(package): update sinon to version 9.0.1

Closes #45

Author: greenkeeper[bot]

package.json

@@ -55,7 +55,7 @@
     "nyc": "^15.0.0",
     "request": "^2.88.0",
     "request-promise": "^4.2.5",
-    "sinon": "^8.1.1",
+    "sinon": "^9.0.1",
     "sinon-chai": "^3.4.0",
     "swagger-parser": "^8.0.4"
   },