chore: added commitizen

Signed-off-by: Sebastian Haas <sebastian@haas.tech>

package.json

@@ -56,6 +56,7 @@
   "devDependencies": {
     "browserify": "^14.0.0",
     "chai": "^3.5.0",
+    "cz-conventional-changelog": "^2.0.0",
     "grunt": "^1.0.1",
     "grunt-browserify": "^5.0.0",
     "grunt-contrib-clean": "^1.0.0",
@@ -86,5 +87,10 @@
     "typedoc": "^0.5.7",
     "typescript": "^2.2.1",
     "typings": "^2.0.0"
+  },
+  "config": {
+    "commitizen": {
+      "path": "./node_modules/cz-conventional-changelog"
+    }
   }
 }