WIP: Add version information to edges of berks viz

This branch patch successfully adds version information to the edges of the nodes in `berks viz`.

Unfortunately, the berkshelf README doesn't include information on how to run the tests and I am new to ruby so I don't know how to get started. If that information is added somewhere, and this functionality is wanted, I'd be happy to clean this up to get it included upstream.
So - I believe it should be a requirement that we run these tests. Travis allows us to install dot as part of a `before_install` and developers should have dot installed to run these tests.