Vagrant-builder should be able to bake custom Atomic images

[purpleidea]

After talking with https://github.com/rwmjones it appears two bugs are currently blocking atomic+virt-builder and these should be fixed so that developers can hack on atomic more easily, along with many more use cases. The two bugs are:

https://bugzilla.redhat.com/show_bug.cgi?id=1102241
https://bugzilla.redhat.com/show_bug.cgi?id=1177460

Beverages, eternal fame or other prizes will be awarded to whoever gets these fixed :)

This would also be an easy way to keep developers happy, as they could have whatever custom tools they want in their own spins and images. These two bugs are also mentioned in: purpleidea/oh-my-vagrant#78 (comment)