Add post count, image count, and unique posters to post detail

Just like 4chan has!!!!!!!

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

board/templates/board/post_detail.html

@@ -29,6 +29,15 @@
 </div>
 {# return links #}
 [ <a href="{% url 'board:board_detail' board.url %}">{% translate "Return" %}</a> ]
+{# posts / images / poster count / page #}
+<span class="post_stats">[
+    <span title="{% translate 'Post replies' %}">{{post.replies.count}}</span>
+    /
+    <span title="{% translate 'Image replies' %}">{{post.image_replies_count}}</span>
+    /
+    <span title="{% translate 'Unique posters in this thread' %}">{{post.unique_posters}}</span>
+    ]
+</span>
 <hr />
 {# posts #}
 <div class="row post">