Updates Vagrantfile 'ansible.limit'

* Changes ansible.limit from 'all' to 'play_vagrant'
* Updates ansible_hosts to match ansible.limit setting

The change is intended to limit ansible to applying only to this single
Vagrant box rather than all ansible managed boxes.  Because caution.
Merge pull request #4 from jeremykendall/master

Updates Vagrantfile 'ansible.limit'