Use xml_escape for the RSS description content vs strup html

feed.xml

@@ -17,7 +17,7 @@ layout: null
                 {{ post.url | prepend: site.url }}
             </link>
             <description>
-                {{ post.content | strip_html }}
+                {{ post.content | xml_escape }}
             </description>
             <pubDate>{{ post.date | date_to_rfc822 }}</pubDate>
             <guid>