Animated Blocks (0.6.0 Alpha)

This update is really exciting!  It's something I've wanted for a long time and it's finally happening: animated blocks!  Squee!

For a basic example, I added a fire block that tumbles like sand and gets destroyed by contact with water.  I admit that the art needs a bit of work, but that will take some time, as I'm not that great of an artist and most art I've found for fire doesn't tile at all.