Merge pull request #25 from quora-wings/master

README made into Markdown, prettiness preserved (closes #24)
A few formatting changes to README.md
Implement client and s2s INVITE commands
Allow channel entry based on invite lists (closes #17)
Move /LIST +p +s test to list_entry.

This prevents an entry from being printed with /LIST #channel when
the channel is +p or +s.