Instead of printing the error to stdout return the error to the user.
This may not be a hard error (as later certificates would have passed)
but it never is good to be in a state where you have certificates in a
broken state.
Resolves#586
Let's pull off the bandaid!
* Reduces studdering: webrtc.RTCTrack -> webrtc.Track
* Makes it easier to find types by editor autocomplete
* Makes code read more fluently (less repetition)
Since we're breaking the API in 2.0, our only chance to
do this is now.
Relates to #408
