Customization of PS1 prompt

username color now indicates battery level (green, yellow, red)

widget to show branch name as well as status of git repo:
  clean - green
  uncommitted changes - yellow

placeholder for mail alert:
  at sign should appear when new mail in inbox from mutt
Removed line numbers from vim

Wasted width, line is displayed at bottom and to jump to a line use :<number>
Easier split resize keybindings
Added hint for maximizing/minimizing/equalizing splits
Keybindings for py.test: current file and full suite