List security update

[Bozidar Jerkovic <bozidar AT salilab.org>]

Hi all,

Since the spammers didn't give up I needed to act again. This time I have
implemented restrictions on posting messages. From now on only the
subscribers can post to the list. I also increased a number of keywords that
are monitored for spam content, so please make sure that you don't use any
stock market terminology when posting to the list.

Thanks for your patience once again...

Best,
Bozidar