Make audio files auto-complete when /play typed in chat area.

![screen shot 2014-09-14 at 3 07 05 am](https://cloud.githubusercontent.com/assets/93607/4263329/cc9cb9b0-3bdd-11e4-83f8-fd489ded297b.png)

I think only ding.wav and threetone-alert.wav are there by default, might be good to not include the others referenced here.