Custom theme with Git support

This is my personal oh-my-zsh theme. It has Git support through
methods found in Git lib file of oh-my-zsh. It uses:

- parse_git_dirty()
- git_prompt_ahead()
- current_branch()
- git_prompt_short_sha()
- git_prompt_status()

It also shows user name, machine name and current path. You can
take a look at a screenshot at http://goo.gl/ZVoyk