Fix #126. Incorporate the repoze timeago function as a new 'elapsed' template filter. This should save space in the shoutbox when displaying dates. Also used in the new posts forum template tag.

{% if show_button %}
<a href="{% url forums-edit_post id=post.id %}"><img src="{{ MEDIA_URL }}icons/page_edit.png" alt="Edit post" title="Edit post" /></a>
{% endif %}