Vagrant no longer supports RubyGems as an installation method

See also http://mitchellh.com/abandoning-rubygems
Update Vagrantfile to version 2
berkshelf must installed as vagrant plugin

Bundler is no longer necessary
Update testing / developing section
Update vagrant doc link to version 2
Update use ssh (add box names)
Merge pull request #1 from tuxinaut/master

Update for new Vagrant and Berkshelf (plugin) version