Need Vagrant to be ok with bundler 1.7

This hasn't been released in a tag yet, so I'll go straight to the commit: 'https://github.com/mitchellh/vagrant/commit/bb22a37ed1989403e25e889d913b512090a5737f'
Merge pull request #13 from petems/fix_bundler_dependancy_issue

Need Vagrant to be ok with bundler 1.7