Clean up recipes tarball when downloading a github source tarball

It would be nice to be able to download recipes directly from github without having to tar things up manually and drop the recipes on a server somewhere (S3, github downloads etc).

For example, I'd like to be able to download from http://github.com/mikehale/cookbooks/tarball/master instead of http://github.com/downloads/mikehale/cookbooks/cookbooks.tar.gz.

The problem with downloading from a github tarball link is that it creates a base folder named something like mikehale-cookbooks-6dfc8fd.

It should be pretty easy to detect that the recipe_url is downloading a github source tarball and change the base folder name to cookbooks.