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 
@jakedavis ah, ok. In that case, you can do this:

```
group :integration do
  cookbook 'apt'
end
```

We do the same thing for a number of cookbooks that we test using TK.