Expanded detail on TLS mapping, added references.
Merge pull request #225 from gdamore/tls-edits

Expanded detail on TLS mapping, added references.
Remove Martin Sustrik from authors of TLS RFC.

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
Fix how errno is set up by nn_poll().

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>