Add Multiple OS capability and update puppet modules

For clients running CentOS servers, it is best to test on similar vagrant-boxes due to differences in packages (versions and patches) and configuration.

This branch updates all the puppet modules, and then adds the option to select CentOS as the vagrant box OS.
The box used comes from Puppet Labs, which unfortunately only has an 8GB disk. This can be problematic when testing larger Drupal sites with lots of files, but I will submit an issue/pull request at https://github.com/puppetlabs/puppet-vagrant-boxes to see if we can't get them to build their boxes more similarly to the files.vagrantup.com precise64 box.

Comments welcome.