bug fix in gif. added cat demo. starting python game.

1. there was a bug on the display when resizing. fixed the bug by centering the image 
2. add a simple demo with a cat gif. will run out-of-the-box
3. started working on a snake game on the matrix --- not yet open source. will open source upon receiving permission 
4. changed everything to use wishbone interface for performance. keep frame buffer and do one io call per frame instead of per pixel.