Make a dummy CheckersRoom class.
Implement checkers model.

I have no idea if this works.
Rewrite Checkers to use the new interface.
Add the test suite.
Add implementation of some tests. They fail.
Implement the tests
Rename checkers spec
Use better matching.
Fix the basic tests.
Make more tests pass!
Got position validity working.
Do a quick fix.
Rebase Checkers with updated model stuff.