0.1.2

Patch release; the codec is unchanged since 0.1.1.

• examples/client.py — a listen/send client against cantcpd (plain or TLS 1.3 with mutual TLS);
• the examples wrap sockets correctly (makefile("rb", buffering=0), explicit flush) — the previous ones could block on a single frame;
• README/CONTRIBUTING document the stream requirement and the canon sync.