chore(package): update sinon to version 8.0.1

Closes #26

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
     "istanbul": "^0.4.5",
     "jsdoc": "^3.4.3",
     "mocha": "^5.0.0",
-    "sinon": "^5.0.0",
+    "sinon": "^8.0.1",
     "webpack": "^4.0.0"
   }
 }