[test-kitchen] update project to support 1.0.0.alpha.1

* Use Vagrant 1.1.x is now installed via the native installer
* Remove `Gemfile`:
  * Vagrant is no longer pulled in as a library.
  * The `berkshelf-vagrant` plugin is now installed directly into the 
    Vagrant installation.
* Remove `Vagrantfile` - test-kitchen now generates a `Vagrantfile` for 
  each platform/suite combination.
* Update `.kitchen.yml` for new Vagrant 1.1 network format
[COOK-2574] Incorrectly referenced attribute

Not sure how I missed this in the template.
Merge branch 'COOK-2574'