Docstrings don't have to be enclosed in triple quotes; update GPL
exception to apply to all strings to reduce confusion and licensing
issues.

* Rename IrcBot to IRCBot.
* Replace target parameter with channel in on_message() and on_notice().
* Remove is_self parameter from events.
* Add message parameter to on_kick().
* Remove is_alive().
* Change send_raw() parameters to an IRC command and a list of arguments to the
  command.
* Rename on_other() to on_raw().
* on_raw() is now called for every IRC message, not just ones without a
  specific event.
* Remove async_events parameter from listen() and listen_async().

* Add IStr, a case-insensitive string class.
* Add IDefaultDict, a case-insensitive dictionary class.
* Make all nickname, channel, and target parameters in events case-insensitive.
  See IStr for more information.
* Add IRCBot.nicklist, a case-insensitive dictionary which stores lists of
  users in channels.
* Make IRCBot.channels case-insensitive.
* Make IRCBot.nickname case-insensitive.
* Add a timeout parameter to wait().
* Add a realname parameter to register().
* When given a list of CA certificates, make connect() verify the server's
  hostname as well as its certificate.

* Rename some private methods.
* Rename some private buffers.
* Make methods call send_raw() instead of writeline().
* Handle socket errors more gracefully.
* Make parse() a static method.
* Add format(), which formats IRC messages.
* Make register() wait for RPL_WELCOME instead of MODE.