Update Vagrant Completion to 0.0.5

Tested:

```bash
brew install https://raw.github.com/petems/homebrew-completions/patch-2/vagrant-completion.rb
######################################################################## 100.0%
==> Downloading https://github.com/kura/vagrant-bash-completion/archive/0.0.5.tar.gz
######################################################################## 100.0%
==> Caveats
Bash completion has been installed to:
  /opt/boxen/homebrew/etc/bash_completion.d
==> Summary
  /opt/boxen/homebrew/Cellar/vagrant-completion/0.0.5: 3 files, 16K, built in 2 seconds
```

Also fixes https://github.com/Homebrew/homebrew-completions/issues/8