Add RTCRtpSender, RTCRtpSender, and friends
Respond to CR comments
Merge anchor fix from @dontcallmedom
AddTrackEvent -> RTCAddTrackEvent

Fix the parameter descriptions for RTCAddTrackEvent
PR feedback; onaddtrack -> ontrack
Merge pull request #18 from juberti/master

Merge juberti:master to doohickey branch