[H-ADMIN] Non Australian IP's can no longer create a Humbug Wiki account

[Russell Stuart]

In the past week or so there have been around 200 failed attempts to
create an account on the Humbug Wiki, all as far as I can make out by
spammers.  They have all failed, of course, but they have all generated
an email to the exec and I've gotten the shits will all these emails.

So, I've altered the EmailActivation code to ignore people who don't use
a @humbug.org.au address and don't have an Australian IP address.