chore(package): update sinon to version 7.3.1

Closes #20

Author: greenkeeper[bot]

package.json

@@ -45,7 +45,7 @@
     "mocha-sinon": "2.0.0",
     "nyc": "11.0.3",
     "semantic-release": "6.3.6",
-    "sinon": "2.3.6",
+    "sinon": "7.3.1",
     "sinon-chai": "2.11.0",
     "validate-commit-msg": "2.12.3"
   },