Fix tests
Fix tests

Puppet <3.6 can't do ruby 2.1 because of issues fixed in:
https://github.com/puppetlabs/puppet/pull/2184/files
https://tickets.puppetlabs.com/browse/PUP-1243

So explicitly test 3.6, though this is a candidate for removal.

Puppet 2.7 is EOL as of last september:
https://groups.google.com/forum/#!msg/puppet-users/8JEy7wY5VPs/9N07fgfU1mAJ

icalvete/puppet-graphite,icalvete/puppet-graphite,icalvete/puppet-graphite