Ignore the vendor folder in Cmd-T listing.

This is literally and figuratively the greatest thing to happen to my
happiness level since I started contracting with GitHub. THANK YOU
@nixterrimus!

Ref: http://blog.dcxn.com/2013/10/22/faster-ctrlp-dot-vim-for-rails/
Merge branch 'master' of github.com:parkr/dotfiles

* 'master' of github.com:parkr/dotfiles:
  Update comments to reflect current code.