chore(package): update sinon to version 5.0.6

Closes #25

Author: greenkeeper[bot]

package.json

@@ -47,7 +47,7 @@
     "mocha": "^5.0.0",
     "mock-require": "^3.0.0",
     "nyc": "^11.4.0",
-    "sinon": "^4.1.3",
+    "sinon": "^5.0.6",
     "sinon-chai": "^3.0.0"
   },
   "nyc": {