Also look for dotfiles-local

While trying out the approach outlined in Croaky's latest [blog post], I
realized that running `rcup` would not also pull updates from my local
extensions. If you clone your extensions as `dotfiles-local`, this
update will pick them up.

Non-existent directories are ignored by rcup, so it won't cause issues
if you don't have `dotfiles-local`.

[blog post]: http://robots.thoughtbot.com/manage-team-and-personal-dotfiles-together-with-rcm
Preliminary changes to thoughtbot dotfiles

* Add vim plugins for tmux, ag, i18n
* Add tmux shortcuts for splitting, resizing, and moving between windows
* Improve tmux copy/paste
Some modifications to dotfiles

* Plugin to autoclose parens, brackets, quotes, etc.
* Set cdpath for easy directory switching
* Set cursor line and 80 character lines in vim
* Misc git and zsh aliases
Add shortcuts for blank line insertion and search with Ag
Summarize modifications to thoughtbot dotfiles in readme
Add git-promote script