Added vagrant-aspen playbook and vagrant conf

@jarv, can you review this? I'm in the process of testing, to be sure that this works the way I expect. (I mostly copied the vagrant file from `vagrant-fullstack.yml`.)
Why don't we need the release version of this file updated too? (as in https://github.com/edx/configuration/blob/master/vagrant/release/fullstack/Vagrantfile)