Merged #37 and RTCMultiConnection-v1.3 testing demo added

https://webrtc-experiment.appspot.com/RTCMultiConnection-v1.3/

According to #37 by @FreCap:

"Everyone has a laptop, if he has an high volume, will be killed by
echoes.

Sometimes Firefox crashes while echoing and you have to hard reboot your
PC ( Ubuntu 13.04, FF 21 )"

So, local media streams are now "muted" by default (in all
RTCMultiConnection releases).