Generalize .kitchen.yml

[mikelococo]

Test-kitchen is integration testing, but currently has a fairly idiosyncratic provider setup involved vagrant, vagrant-lxc, and polipo caching. This will break test-kitchen for anyone not running linux, not using lxc, and not running polipo for caching... this is essentially everyone. Generalize .kitchen.yml so it will work on a Vagrant/Virtualbox setup without polipo, which is the most common.

@mikelococo will likely look into this someday, but PR's on would be gladly accepted.