RTCDataConnection library added

https://bit.ly/RTCDataConnection

RTCDataConnection is a library sits top of RTCPeerConnection and
RTCDataChannel to bring easiest file and data sharing experience.
RTCDataConnection auto-handles multi-user data connectivity like file
broadcasting or group file sharing.

Demos using RTCDataConnection:

https://googledrive.com/host/0B6GWd_dUUTT8RzVSRVU2MlIxcm8/RTCDataConnection/