chore(package): update sinon to version 7.3.1

Closes #57

Author: greenkeeper[bot]

package.json

@@ -70,7 +70,7 @@
     "husky": "^0.14.3",
     "nyc": "^12.0.2",
     "rimraf": "^2.6.2",
-    "sinon": "^6.1.3",
+    "sinon": "^7.3.1",
     "validate-commit-msg": "^2.14.0"
   },
   "ava": {