Button for channel names.

* weechat-button.el: new `weechat-button-list' entry for channel
  names.
* weechat.el: `weechat-join' function.

Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
Changed `weechat-handle-color-codes' into iterative code.

Fixes "Lisp nesting exceeds `max-lisp-eval-depth'" error.

Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
Merge pull request #13 from ruediger/master

Button for channel names.