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/137686/1968582/fa41b3d2-82e4-11e3-910a-4bc2ce2d526d.gif)