Updates client_api_version to 3 with puppet >= 3.6.0

Previously the client_api_version was only set to 3 with PE >= 3.2.0
PMT in Puppet >= 3.6.0 also requires the v3 forge api.
Merge pull request #211 from adreyer/puppet-v3-compat

Updates client_api_version to 3 with puppet >= 3.6.0