Fixed vim alias.

- Only set vim alias if MacVim is installed (using homebrew or not)
Merge pull request #235 from rafaelregis/fix_vim_alias

Fixed vim alias.
Add quickfixsigns module - shows which lines changed
Merge remote-tracking branch 'upstream/master' into customizations

* upstream/master:
  Add quickfixsigns module - shows which lines changed
  Fixed vim alias.