FEATURE: Show dismiss posts/topics buttons on category filtered lists

FEATURE: Add Dismiss Posts/Topics button to Category filtered Unread View
![image](https://cloud.githubusercontent.com/assets/2060315/4762124/30466abc-5afe-11e4-8e9e-807694c9f091.png)

```
if params[:category_id]
+        topic_ids = TopicQuery.unread_filter(tq.joined_topic_user).listable_topics.where('category_id = ?', params[:category_id]).pluck(:id)
+      else
+        topic_ids = TopicQuery.unread_filter(tq.joined_topic_user).listable_topics.pluck(:id)
+      end

```

```
topics =  TopicQuery.unread_filter(tq.joined_topic_user).listable_topics
topics =  topics.where('category_id = ?', params[:category_id]) if params[:category_id]
topic_ids = topics.pluck(:id)
```