chore(package): update commitizen to version 4.0.4

Closes #40

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
     "@babel/register": "^7.4.4",
     "ava": "^2.1.0",
     "browser-env": "^3.2.6",
-    "commitizen": "^3.1.1",
+    "commitizen": "^4.0.4",
     "conventional-changelog-cli": "^2.0.21",
     "coveralls": "^3.0.4",
     "cz-conventional-changelog": "^2.1.0",