I420 format is a common format that's required by encoders. Therefore,
the video pipeline is significantly faster than other formats since
there's no format conversion.
With webrtc v3, users no longer need to bind or unbind manually anymore.
Changes:
* Switch from webrtc.RTPCodec to webrtc.RTPCodecParameters
* Fix broken examples after the upgrade
* NewRTPReader now accepts ssrc as a parameter
* Track interface now fulfills webrtc.TrackLocal requirements