chore(package): update sinon to version 8.0.0

Closes #337

Author: greenkeeper[bot]

package.json

@@ -79,7 +79,7 @@
     "regenerator-runtime": "^0.10.3",
     "replace-bundle-webpack-plugin": "^1.0.0",
     "script-ext-html-webpack-plugin": "^2.0.0",
-    "sinon": "^4.2.1",
+    "sinon": "^8.0.0",
     "sinon-chai": "^2.9.0",
     "source-map-loader": "^0.2.1",
     "style-loader": "^0.21.0",