Add a script to post sound messages on Hall's rooms

This script uses Hall's API to send an message with HTML5 audio tag
Hall: www.hall.com

Post sounds with autoplay disabled is just for fun and make the room more interactive!

With it you'll be able to record sounds links with key like:
*hubot record sound sample www.fakewebsite.com/sample.mp3*
and post:
*hubot sound me sample*