Add GhettoBerryBlast.tmTheme and update themes.json and README.md

Submission of GhettoBerryBlast theme.
![screenshot from 2014-12-15 03 18 16](https://cloud.githubusercontent.com/assets/6887698/5433060/23f72498-8409-11e4-8bd5-2b7f02e917b5.png)