Start a new Game

If you remember our originally planned behavior, and I don't blame you if you don't, we wanted to draw a new game button on the screen when RHB crashed and fell over. Then, when it's clicked, we want to start a new game. For that to happen, we'll need to do the following:

1. Check whether RedHatBoyStateMachine is KnockedOut, and if so, transition from Walking to GameOver.
2. On that transition, draw the new game button.
3. Add an onclick handler so that when the button is clicked, we transition back to Ready with a new Walk instance.
4. On the transition to Ready, hide the button and restart the game.

All the code we wrote before was to make that change easier. Let's see whether we were right about that:

1. Transition from Walking to GameOver.

To transition from Walking to GameOver, we need to return the GameOver state from the WalkTheDogState<Walking> update method, but when should we do that? We'll need...