Put TicTacToeModel in TicTacToeRoom.

- Delete TicTacToeModel.scala
- Everything is in the TicTacToeRoom object.
- TODO: renaming.
Refactor tictactoe room for conciseness.

- TicTacToeState => State
- TicTacToeTurn => Move
(these are specific to the TicTacToe file, so no name pollution is
occuring)