Rename test directories to match Rails 4 standards
Remove validates_associated :client

I'm pretty sure I didn't really understand what that did when I added it.
Move compression to EtchConfig.

Putting the compression in the etch library was stupid, it belongs in
the model.

Also update a bunch of find_or_create_by calls.
Update a find_or_create_by call
Update rake
Add some unit tests for models

Etch has a comprehensive integration test suite, but having some basic
unit tests in the standard Rails format seems like a good idea.