Fix problem when deleting multiple topics from a forum in bulk. We getting a list of topics from the database, then deleting each topic. But after you delete a topic, the forum.last_post on the remaining non-deleted topics can be stale. This was causing a weird DoesNotExist. Now just get the topics one at a time from the database.

Dear {{ to_name }},

Your friend, {{ sender_name }}, wanted to send you a link to an 
interesting story found on {{ site_name }}.

{{ story_title|safe }}
http://{{ site_url }}{{ story_link }}

Thanks!
http://{{ site_url}}