@Kabouik reports in #211

I think the issue might be related to Gitter rooms being formatted with a slash in their name, which must conflict with the way tiny sets filenames for logs. You can see above in my configuration file that the channel I wanted to join on irc.gitter.im was "#jarun/nnn". If this is really the cause, then perhaps an acceptable workaround would be to replace / with another character when creating new log files, such as -?

In other words when the channel name contains / logger fails to create the log
file and reports this in "mentions" tab:

Logger error: Os { code: 2, kind: NotFound, message: "No such file or directory" }

Two TODOs:

• The error message should show the file path
• We should handle channel names with /s in them (as far as I can see RFC 2812 allows this)