Changed coins after ramp

Distance between coins is dependent on Object.speed. New method in
SnowWorld: addObject2(Actor a, int x, int y). It will add the actor at
(x,y) if there isn't already an Object there. Changed the snowman and
ramp images to have less empty space around their edges. This should
help ameliorate some collision problems. Changed the music file to
Tyeler's edited version.