Add link for RSS subscription

lib/site_template/index.html

@@ -9,4 +9,7 @@ layout: default
       <li><span class="post-date">{{ post.date | date: "%b %-d, %Y" }}</span> <a class="post-link" href="{{ post.url }}">{{ post.title }}</a></li>
     {% endfor %}
   </ul>
+
+  <p class="rss-subscribe">subscribe <a href="/feed.xml">via RSS</a></p>
+
 </div>