rewrite topics routes to include id

app/templates/threads/thread.html

@@ -5,7 +5,7 @@
 {%- block content -%}
 {%- set td -%}
 <ul class="horizontal">
-<li>Started by <a href="{{url_for('users.user_page', username=started_by.username)}}">{{started_by.get_readable_name()}}</a> in topic <a href="{{url_for('topics.topic', slug=topic.slug)}}">{{topic.name}}</a></li>
+<li>Started by <a href="{{url_for('users.user_page', username=started_by.username)}}">{{started_by.get_readable_name()}}</a> in topic <a href="{{url_for('topics.topic_by_id', topic_id=topic.id)}}">{{topic.name}}</a></li>
 {%- if thread.locked() or thread.stickied() -%}
   {%- if thread.locked() -%}
   <li class="visible">Locked</li>