Start screen implemented. Game now starts paused, then GameRestartEvent (which should really be renamed to GameStartEvent, Leigh was right) unpauses the game after the user presses spacebar. Scales to fit full screen, which doesn't look great but good enough for now.
win_lose_message deprecated in favor of win and lose screens.
Implemented the story screen.
Merge pull request #90 from fenaren/start_screen

Start screen implemented. Game now starts paused, then GameRestartEvent ...