Add reply highlighting and post reply list.

If a user hovers over a reply link to a post, it will highlight that
reply (if it exists). Also, all replies to a post (that are visible) are
added as another element to that post.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

board/templates/board/post_snippet.html

@@ -19,7 +19,7 @@
     {% endif %}
 
     {# Post ID, status icons, username, time, admin info #}
-    <a href="#p{{post.id}}">#.</a>
+    <a class="post_permalink" href="{{post.get_absolute_url}}">#.</a>
     <span class="post_id">{{post.id}}</span>
     {% if post.subject %}
         <span class="post_subject">{{post.subject}}</span>