Added fullscreen option to IDE and favicon

New fullscreen or "zen mode" added to the code editor. 
Added a CloudPebble favicon because the lack of one was bugging me.
![cloud_pebble_fullscreen_demo](https://f.cloud.github.com/assets/137686/1968619/8743211c-82e5-11e3-823b-0a2cfe4ce832.gif)