Improve the drawing example

Improves the drawing example by introducing the following changes:
* Buttons that modify brush size and color
* Eraser-tool
* Custom cursor that changes based on brush size and color

Also updated the JSFiddle, which can be found [here](http://jsfiddle.net/57Nbx/). 

Minor changes:
* TogetherJS now auto-starts
* TogetherJS clicks are now hidden for everything except the canvas

The example uses font-awesome through a CDN.

Screenshot:
![image](https://f.cloud.github.com/assets/3536982/1704681/44ec401a-60cf-11e3-8b86-7470ccd1e375.png)