chore(package): update sinon to version 8.1.0

Closes #164

Author: greenkeeper[bot]

package.json

@@ -86,7 +86,7 @@
     "redux": "^4.0.1",
     "redux-mock-store": "^1.3.0",
     "redux-thunk": "^2.2.0",
-    "sinon": "^7.3.2",
+    "sinon": "^8.1.0",
     "sinon-chai": "^3.3.0"
   }
 }