Added a custom tag to display a link to a profile. Refactored the avatar tag to optionally display a profile link around the image. Removed the width and height attributes from the avatar image tag. I think this was causing disk hits whenever those properties were not cached. The avatar tag is now an inclusion tag.

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}}