Logging broken for channels that contain /

[mshade]

Willie spews errors when trying to log channel activity for channels that contain a '/' in the name. It interprets the / in the channel name as a subdirectory when trying to write.

For example, in the channel #r/linux on freenode:

IOError: [Errno 2] No such file or directory: u'/home/willie/chanlogs/r/linux-2015-02-13.log' (file "/home/willie/willie/willie/modules/chanlogs.py", line 113, in log_message)

[embolalia]

Duplicate of #490.

[mshade]

Apologies, searching for '/' is a little difficult :)