Custom StarlingEventMap Implementation

This is a solution based on issue #4. Basically, I cloned the Robotlegs map (because it's difficult to extend) and added a couple of new methods based on a new interface called IStarlingEventMap:

```as3
package org.robotlegs.core
{
	import starling.events.EventDispatcher;

	public interface IStarlingEventMap extends IEventMap
	{
		function mapStarlingListener(dispatcher:EventDispatcher, type:String, listener:Function, eventClass:Class = null):void;
		function unmapStarlingListener(dispatcher:EventDispatcher, type:String, listener:Function, eventClass:Class = null):void;
	}
}
```

I also made some tweaks to the MediatorMap to be able to extend it a lot easier in case your view structure is a little different from the norm. :)