Enable tmux to send-prefix using C-a a

* It's useful when you have a tmux session into another tmux session
  (ie. via ssh).
Removed sparkup from readme [Fix #403]
Add puppet module
Fix gitconfig colors causing iTerm with solarized to show diffs incorrectly
Changed reference to prezto master
Go back to using skwp prompt for rvm-prompt integration
Merge pull request #402 from imobach/master

Enable tmux to send-prefix using C-a a
Merge branch 'master' of https://github.com/skwp/dotfiles

* 'master' of https://github.com/skwp/dotfiles:
  Go back to using skwp prompt for rvm-prompt integration
  Changed reference to prezto master
  Fix gitconfig colors causing iTerm with solarized to show diffs incorrectly
  Add puppet module
  Removed sparkup from readme [Fix #403]
  Enable tmux to send-prefix using C-a a