chore(package): update sinon to version 4.0.0

Closes #47

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
     "mocha": "^3.1.2",
     "react": "^15.3.0",
     "react-dom": "^15.3.0",
-    "sinon": "^2.0.0",
+    "sinon": "^4.0.0",
     "standard-version": "^4.0.0",
     "webpack": "^1.13.1"
   },