Factor out Exhibitor

This PR is a massive change to accommodate the new [Exhibitor cookbook](). It will be a full version bump to 2.0.0, but is now a pre-release. I'll test for the next day or two both this and Exhibitor (and clean up both), and I intend to make this a LWRP, probably maintaining a default recipe to keep backwards-compatibility.

Supercedes #76 
Hmmm, yeah the apt case is funny. That's in there to accommodate the test kitchen run list. It's not a direct dep for ZK though.

Good point about Berks 3. Haven't touched it yet, but will make this change.