(PDB-552) Pin support for Puppet to 3.5.1 and above

A bug with environments was solved in Puppet 3.5.1, so for the best results we
are pinning against that release version now.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #926 from kbarber/ticket/master/pdb-552-puppet-351

(PDB-552) Pin support for Puppet to 3.5.1 and above