Update git-completion.bash
Lots of changes.

1. Steal some alias and function from http://www.pixelbeat.org/settings/
   ord(), chr(), strerror(), tail, head
2. Add pythonbrew
3. Given "git" the shortest alias "g" :)
Steal some handy mapping from http://www.pixelbeat.org/settings/.vimrc
Switch to 'ervandew/snipmate.vim' to resolve "Attempts to complete at the start of a line"

Ref: https://github.com/ervandew/supertab#frequently-asked-questions
Update vundle submodule.