Added requirement on commit messages
Review comments from Ciprian Dorin Craciun

- ZAP strings are limited t0 255 chars and are ASCII
- ZAP PLAIN credentials take two (string) frames
- RFCs 23, 24, 25, 26, 27 explicitly refer back to previous relevant RFCs
- message id -> request id, and blob instead of string
Added socket type semantics
Clarified error handling
Added some semantics for each command
Added topics for discussion
Added notion of stable public contracts
Various clarifications for implementors
Moved all topics for discusison to the end
New RFCs for socket type semantics
Added RFC 32 and LICENSE for reference code
Finished draft of socket type semantics

- separate RFCs for each pattern
- formal language to define socket behavior
- removed RFC status from headers, it should be set by tag in RFC site
Added PING, PONG to RFC 23.
Merge pull request #21 from hintjens/master

Updated RFCs