remove comma at the end

Author: Karthik Kumar A

README.md

@@ -111,7 +111,7 @@ In Angular 2/4 cli projects, modify **.angular-cli.json** as below:
 
       "styles": [
         "styles.css",
-        "../node_modules/ng2-tree/styles.css",
+        "../node_modules/ng2-tree/styles.css"
       ],
 ```
 4. And finally, I suppose, you'd want to listen to events generated by ng2-tree (for a full list of supported events look at the [API](#wrench-api)). No problem, this is also easy to do - for example let's add a listener for `node was selected` kind of events: