chore(package): update sinon to version 8.0.2

Closes #98

Author: greenkeeper[bot]

package.json

@@ -40,7 +40,7 @@
     "nyc": "^12.0.2",
     "prettier-standard": "^8.0.1",
     "rimraf": "^2.6.1",
-    "sinon": "^6.1.5",
+    "sinon": "^8.0.2",
     "sinon-chai": "^3.2.0",
     "standard": "^10.0.0"
   },