webrtc-pc

abdf3e58 - Update paragraph that introduces senders/receivers/transceivers.

Update paragraph that introduces senders/receivers/transceivers. Fixes #1241. This paragraph hasn't been updated much since the transceiver model came about (aside from basic find/replace), so it was a bit out of date. It was implying that receivers could be created independently from transceivers, which is not the case.