(PDB-3917) Gemfile: refer to puppet via :ref not :branch
(PDB-3917) Gemfile: refer to puppet via :ref not :branch

This should be more appropriate, since we'll want to be able to use
tags and hashes too.

puppetlabs/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,rbrw/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,rbrw/puppetdb