Changes to merb_global posting settings

[myabc]

This group has received a deluge of spam the last several weeks. Our
previous spam settings were that messages from non-members would be
moderated. Hopefully such messages have been caught and have never
reached your Inbox. I find myself having to clean out the moderation
queue a couple times a day though.

As such, I've changed the group settings as follows:

- you'll have to be a member of the group to post messages.
- if you're a new member, then messages will be moderated.

I realise the group isn't very active presently, but I do know that
there are people using merb_global in their applications, and so I
wasn't inclined to take the extreme approach and shut down/move the
mailing list/discussion group.

Many thanks