Update credits to include beta testers

So much love for @michaelglass @andymoe @somekittens and @ctwiz
for testing this app out.
Actually /part channels when you close the tab
Add channel to server when saving it

I strongly suspect this would persist the channel but for the
current run, the list of channels for the server would NOT change.
Update sidebar when users change their nick, part or join

Also, correctly parse the users /NICK line