Prepare Puppet modules and manifest prior to provisioning with Vagrant

@zined Here we go.

This is a prototype which incorporates the work I've been doing in https://github.com/Jimdo/puppet-skeleton/pull/1

Running `rake vagrant:provison` will set up the Puppet modules with Librarian-Puppet before provisioning with Vagrant. You can add arbitrary dependencies to `Puppetfile`.

(The generation of the manifest is a bit hacky, but should do for now.)

Looking forward to your feedback. :)