Setting up tests; wrote basic test to drive out new DefenseBoard class
Started DefenseBoard class to pass tests
First expectation for DefenseBoard: it gets info about ship placement
De-normalizing link between Player and PlayerCoord
Adding #ship_name method to PlayerCoord model
A working test for the occupied coord hash.
Added test for more than one coord; refactored and restructured tests
Use the DefenseBoard to replace User#defense_board call in build_defense_board helper
Update PlayerShip::add_ship to track the de-normalized coord/player relation.
Updated test