Begin writing the IntroAnimator class
Add init() method for IntroAnimator
IntroAnimator: Add reset()
IntroAnimator: Add is_running attribute

Almost forgot.
IntroAnimator: Add move_background_up()
IntroAnimator: Add fade_in_logo()
IntroAnimator: Add FADE_LOGO_RATE constant

Again, unnamed numeric constants are bad.
IntroAnimator: Add skip_intro()
Allow IntroAnimator to handle music playback

Since the music is only played once (when the intro finishes), it makes
sense to have the IntroAnimator class handle it instead of TitleState.