Improved support for comments

A couple of people actually left comments (woo-hoo!!).
This helped me see a number of problems with the comment feature. So I've fixed some things.

• A default title for the comment gets filled in.
• I get mail when people submit comments.
  BULLET - People can leave an email address and subsequent comments on the same article will get sent to them. Of course they can edit their comment and remove the email address.

I still need to record and display the date/time when the comment was made, and maybe even make an 'atom' feed of comments....