Large update

I did a lot of work on fleshing this game out.

Added:

• 4 new levels bringing the total to 8
• A powerup that allows you to rewind time while your character is free to move
• A collectible 'cog' item as some kind of an extra challenge
• 5 songs as well as sound effects
• A title screen
• A visual rewind effect when you rewind
• A level select screen

...and various other things