chore(package): update sinon to version 4.1.5

Closes #17

Author: greenkeeper[bot]

package.json

@@ -49,6 +49,6 @@
     "iced-coffee-script": "^108.0.11",
     "istanbul": "^0.4.4",
     "mocha": "^3.0.2",
-    "sinon": "^3.2.1"
+    "sinon": "^4.1.5"
   }
 }