chore(package): update commitizen to version 4.0.5

Closes #45

Author: greenkeeper[bot]

package.json

@@ -34,7 +34,7 @@
     "test"
   ],
   "devDependencies": {
-    "commitizen": "3.0.5",
+    "commitizen": "4.0.5",
     "coveralls": "3.0.1",
     "cz-conventional-changelog": "2.1.0",
     "eslint": "4.19.1",