chore(package): update sinon to version 7.2.5

Closes #16

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
     "mocha": "^5.0.1",
     "mocha-sinon": "^2.0.0",
     "prettier": "^1.10.2",
-    "sinon": "^4.3.0"
+    "sinon": "^7.2.5"
   },
   "directories": {
     "lib": "lib",