Wiki edit policy change

Hi all,

for a very long time, Ryan James has tirelessly been cleaning up spam
on the wiki, but that's neither fun nor fair nor a wise use of
resources (his time in this case).  We recently realized, with Jarrod
Millman's help, what  the problem was: all the recommended techniques
for disabling Moin account creation (at least the publicly listed
ones) fail hopelessly,  because from any existing logged in user, it
is trivial to trick Moin into auto-generating new user accounts that
it  recognizes.

So instead of the ineffective account creation block, I've changed
things to openly allow new accounts, but without write privileges.
Only users listed here:

http://ipython.scipy.org/moin/WritersGroup

can edit pages.   I went through all the logs I could find to add
everyone I could find that seemed like a valid user, please just let
us know and we'll add you if I missed you.  Please note that anyone in

http://ipython.scipy.org/moin/EditorsGroup

can edit the WritersGroup page and add new names, so it should be
trivial to get added if you want to contribute, just ask here on the
list or email an editor (or me) and we'll add you right away.

Hopefully this will now work, since ACLs in Moin seem to be more
robust than their Gruyère cheese security model for user creation.