Add support for vagrant-cachier plugin

This pull request adds basic support for the [vagrant-cachier](https://github.com/fgrehm/vagrant-cachier). There is no support for [scopes](https://github.com/fgrehm/vagrant-cachier#cache-scope) or targeting specific [buckets](https://github.com/fgrehm/vagrant-cachier#available-cache-buckets) yet.

Attempts to resolve: https://github.com/opscode/kitchen-vagrant/issues/26