Update Berkshelf setup

`vagrant up` was not working for me on this cookbook out of the box.  I went ahead and updated the Berkshelf setup, and now I can jam on vagrant just fine.

* ignore .vagrant
* rename Berkshelf to Berksfile (?)
* modernize Berksfile
* update Vagrantfile to use berks
I figured I'd default the vagrant config to the latest Ubuntu LTS, and I typically use `chef/ubuntu-14.04` for that.

https://vagrantcloud.com/chef/ubuntu-14.04