Feature request: group.playRandom()

This is a handy utility class! One nice feature would be a group.playRandom() function. For example, I may have a group of punch "swooshes" or VO queues that get played when the hero accomplishes something awesome, but I don't want to play the exact same sound every time. It would be nice to be able to create a group of sounds, and then just .playRandom() on that group.

Thanks!
