CHANGES:
- fix: update computation for payload length offset
(#63) - don't select digestif implementation
(#67) - fix: garbled data after committing frame header
(#68) - fix: mask all client frames
(#69) - feat: yield the reader if reads not scheduled
(#70) - unify input handler EOF and websocket error handler
(#70,
#72) - client: fix infinite loop when client handshake disconnects
(#73)