Updating Vagrantfile for API v2

The Vagrantfile appears to be written for an older version of Vagrant.

The Vagrantfile included in this pull request has been updated to use the latest API version ( http://docs.vagrantup.com/v2/vagrantfile/version.html ).

I ran into a problem with the shared folders configuration - this is the Vagrant v2 configuration: http://docs.vagrantup.com/v2/synced-folders/basic_usage.html  I changed the configuration and then had to update the VirtualBox guest additions.

The perlbox base box seems to be built for an older version of VirtualBox, as well.  I used the [Vbguest plugin](https://github.com/dotless-de/vagrant-vbguest) to update the VirtualBox guest additions for my version as shown here: http://kvz.io/blog/2013/01/16/vagrant-tip-keep-virtualbox-guest-additions-in-sync/  I've updated the README with this recommendation.