Rename project to vagrant-librarian-puppet

`gem list -r "\-vagrant"` shows that this isn't a format that's used very often. I can't speak for others, but I tend to look for new vagrant plugins via `gem list -rd vagrant-`, so the current naming might hurt discoverability. And besides, searching for a gem name with `-vagrant` requires some weird escaping.

Just thinking this name-change will be easier to change this early in the game :)