chore(package): update commitizen to version 4.1.0

Closes #15

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "emoji"
   ],
   "devDependencies": {
-    "commitizen": "3.0.6",
+    "commitizen": "4.1.0",
     "greenkeeper-postpublish": "1.1.0",
     "json": "^9.0.4",
     "standard-version": "4.3.0"