[bugfix] Send channel name with add_channel call

This fixes a missing parameter in dispatch_other_join that was causing
a crash in any client when anyone JOINed a channel that the irclib
client was on.

Traceback: https://www.refheap.com/paste/11962
Merge pull request #1 from CorgiDude/fix_join_bug

[bugfix] Send channel name with add_channel call