Switch to jfryman/nginx module

This PR switches from the [ploperations/nginx](https://github.com/puppetlabs-operations/puppet-nginx) module to the [jfryman/nginx](https://github.com/jfryman/puppet-nginx). Both unicorn and thin puppetmaster types are impacted. This would help advance issue https://github.com/puppetlabs-operations/puppet-puppet/issues/100 and get this module closer to a normal forge-based install.

Note that unicorn puppetmasters appear to be semi-broken in the current version of this module. https://github.com/puppetlabs-operations/puppet-unicorn/issues/14 describes the issue and provides a fix. If that's merged in before this is, I'll update this PR to take advantage of it. Beaker tests do not test adequately to catch this problem. (should be addressed, but that's a separate issue)

The only reduced-functionality issue I'm aware of is that this essentially removes the ability to run multiple thin servers and round-robin between them, which can help performance on multi-CPU puppetmasters. That functionality wasn't entirely working previously anyway, so I don't think anybody was using it. If there's demand we can add it back in later.

That said, this is a relatively major change so I wouldn't be surprised if something else broke. This passes rspec-puppet and beaker tests as well as manual testing, but beaker tests currently only test that the services are running and listening on the right ports. They don't actually connect a client to the server.
i'd put this in a variable outside, and just assign it here.