atom.xml applied for PubSubHubbub protocol.

atom.xml

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">

  <title><![CDATA[{{ site.title }}]]></title>
  <link href="{{ site.url }}/atom.xml" rel="self"/>
  <link href="{{ site.url }}/"/>
  {% if site.hub_url %}<link href="{{ site.hub_url }}" rel="hub"/>{% endif %}
  <updated>{{ site.time | date_to_xmlschema }}</updated>
  <id>{{ site.url }}/</id>
  <author>
    <name><![CDATA[{{ site.author | strip_html }}]]></name>
    {% if site.email %}<email><![CDATA[{{ site.email }}]]></email>{% endif %}
  </author>
  <generator uri="http://octopress.org/">Octopress</generator>

  {% for post in site.posts limit: 20 %}
  <entry>
    <title type="html"><![CDATA[{{ post.title | cdata_escape }}]]></title>
    <link href="{{ site.url }}{{ post.url }}"/>
    <updated>{{ post.date | date_to_xmlschema }}</updated>
    <id>{{ site.url }}{{ post.id }}</id>
    <content type="html"><![CDATA[{{ post.content | expand_urls: site.url | cdata_escape }}]]></content>
  </entry>
  {% endfor %}
</feed>