don't read the checksum using the built-in read command, it inserts a ^M that breaks shasum

Rephrase explaining how hosts groups work

Rephrase how to be added to a group

And add some more cases.

we can make this a different and better policy if we want, but now
we have something to start from.

i'm not sure what the best simple phrase is, but 'shared irc host'
might be better