Added forum topic subscriptions

Registered members will now see a link at the bottom of each forum topic page that will allow you to receive e-mail notifications when new posts are added to a topic. 

This is purely an opt-in feature, so nobody will receive mail by default.

As always, keep the awesome feedback coming, and please let me know if you have any problems with the feature.  I'll be subscribed to this topic :)

That's a nice extension, thank you Jason. 

What about RSS feeds? I had one on my iGoogle start page, but it has not been updated since the new forum software has been installed... :-(

Thanks Thierry!  Forum and comment RSS feeds are on my list.  Would you want a feed per topic, per forum, or overall?  (or all 3?)