Migrate db to rename Game columns from player -> user

Update tests and some code in Game model to work with new column names
Create dummy, temp 'black_player' and 'white_player' methods on Game model
that work with existing code by just fetching the new columns. Later, they
will return decorated user objects (Player)
Implement player decorator for users, which know game-specific user info

Refactor lots of code to use the attributes provided by the player decorator

Replace active-record monkeypatch with database_cleaner gem for testing
The 'player passes turn' integration test doesn't pass by itself, god knows why
It passes fine if ran with the other integration tests
Merge branch 'player-decorator'
Fix bug where games lobby doesn't update if empty