Working Guardfile for testing

Since I'd recently set up Guard on my work project, and I'm interested in getting into Shoes4 (since I understand that'll help get Hackety Hack's next version out!) thought I'd take a stab to resolve #407.

Not ready to merge, but I wanted to get it out early for comment and guidance since some of the remaining problems seem a bit thorny.

This does get basic mocked Shoes tests working (wahoo!). Things remaining:

* Swt tests aren't working, I suspect because JRuby isn't started with the `-J-XstartOnFirstThread` flag I see the rake tasks passing along
* Is there a reason that the swt specs are under `spec/swt_shoes` instead of `spec/shoes/swt`? If they were moved there, they'd line up with the production code and wouldn't need their own separate rule in the Guardfile.
* Also have commented out the `pry-nav` gem as it was raising errors in the Guard console every time anything ran. Don't know if removing that is viable, or if I'll need to dig deeper into debugging what's gone bad there.
* Didn't like getting the Coveralls output on every run, but a brief search didn't turn up a way to disable that. Is that an issue?

Any thoughts or pointers on where I should go as I try to get the tests running successfully?