Added curl to UbuntuDeps
Removed deprecated g_thread initialization
Added support to SDES SRTP
Resolved a problem in feedback packets. Now Chrome seems to recover from packet losses
Resolved a problem by which Firefox did not send feedback
Resolved an interoperability problem between Firefox and Chrome
Resolved a bug by which the SDP was exchanged more than once
Decreased CPU consumption. New we use different contexts in Nice, but it seems there is an error when connecting multiple clients (Too many open files).

I reduced the number of transports needed in Sdes to reduce nice connections.

New Licode uses opus. Better interoperability between Chrome and Firefox.
Improved installation in Ubuntu
Fixed compilation for mac
Fixed CMakefile for mac
Updated some files related with screen sharing