Rename to "vagrant-toplevel-cookbooks"

Since the term ["application cookbook" is so much overloaded](https://github.com/berkshelf/berkshelf/issues/535#issuecomment-40890497) in the Chef community I now call the top-level per node cookbooks simply "top-level cookbooks" ([see here](http://lists.opscode.com/sympa/arc/chef/2014-01/msg00419.html)).