Show directory basename in shortprompt
Add publicip function

From http://www.if-not-true-then-false.com/2010/linux-get-ip-address/
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Merge branch 'master' of https://github.com/jrunningen/dotfiles

* 'master' of https://github.com/jrunningen/dotfiles:
  Add MIT license
  vimrc: Remove bufexplorer