Adding VirtualBox support

Adding VirtualBox support along with some port forwarding.
Merge pull request #22 from daviddavis/vagrantfile-update

Adding VirtualBox support
Ensures Puppet 3 is installed from the Puppetlabs repositories.
Merge pull request #16 from ehelms/add-puppet3

Ensures Puppet 3 is installed from the Puppetlabs repositories.
Updating the README

Updating the README to fix the error:

"uninitialized constant Vagrant::Action::Builtin::MixinSyncedFolders"

Looks like it's a < 1.4.3 error.