Allow r10k config & remove Puppet 4 compatability

Fixing tests required a new version of rubocop, which required a new version of Ruby , which Puppet 4 doesn't support. Puppet 4 has been out of support for ages and I think the time has come to drop it.

New Features:

• R10k confic can be created in the root or in spec/r10k.yaml and it will be respected

Removals:

• Puppet 4