Test::Unit cleanup.

There was an error in the documentation/rake task where it wouldn't
actually run all tests.  The new method uses the unix 'find' program
to find all tests, in all subdirectories, under test/. Updated docs and
rake task.

Clean up old tests, and make sure all tests can run properly from within
spork/testdrb.
Create basic provider relationship model with tests.
Update schema.
Implement provider -> provider_relationship association and functionality.
Implement ability to set up and manage provider relationships.
Update migration timestamp.
Remove unused boilerplate test.