Add ChefSpec and Upgrade Resources

* Add ChefSpec and Berksfile for testing.
* Change License to MIT.
* Remove knife:test in favor of ChefSpec catching syntax errors.
* Upgrade Vagrant to latest resources and add plugins. This required
using an install method as described [here](https://github.com/andrewgross/vagrant-chef-zero/issues/41#issuecomment-41112026)
until vagrant-berkshelf catches up to the lates Vagrant version.