Added Tutorial Scene and Fixed Some Bugs

Some people mentioned that the controls were hard to master so we added a Tutorial Level. Also added a Pause Screen, and fixed two bugs. Now the car shouldn't teleport anymore (sorry if you wanted to teleport :P  Tell us if you do and we'll make another game where you can :D ) and when you rewind, the car always goes back the same way.  Thanks to everyone who pointed out the issues!