Rip back out puppet-module-data

Well, it was a nice idea in https://github.com/jfryman/puppet-nginx/pull/453, but there have been several reported issues with the update.

1) Performance hits. This is a bit anecdotal... I've asked for data but have not received any yet. Nonetheless, I have heard from a few folks that introducing `puppet-module-data` adds extra time to catalog compilation.
2) Installation difficulty. I field quite a bit of out of band support requests associated with `puppet-module-data`. It has proven to be hacky enough to cause errors in several edge cases. Because it is not part of Puppet Core, it increases the barrier to entry for a fair number of folks.

I love this pattern, but it need a lot of love, and until it becomes a first class citizen, it needs to be ripped out before we hit 1.0. So, while I hate making a big change and then ripping it out... it's better to do now than before it becomes too unwieldy. 
I did consider this... this is the only variable that didn't seem to match the existing style in the rest of code. I'll put another deprecation warning to make it less painful.