Integration testing with Vagrant

To test the functionality of a Puppet module, we need to run it in Vagrant. While this skeleton already supports `vagrant up`, it does not set up module dependencies yet.

As a solution, I suggest to use librarian-puppet to put *the module and all its dependencies* into place before running Vagrant.

Ideally, we implement something like `rake test:integration`, which I've already done for Chef here: https://github.com/mlafeldt/skeleton-cookbook/

/cc @s0enke @zined