Changes:
* [BREAKING CHANGE] NewEncodedReader is renamed to NewEncodedIOReader
* NewEncodedReader now returns a non-standard buffer reader to give
more meta data such as sample count
Changelog:
* Better support for non-webrtc use cases
* Enable multiple readers
* Enhance codec selectors
* Update APIs to reflect on the new v3 webrtc design
* Cleaner APIs