The Atom feed fails validation at http://feedvalidator.org/ because the `<category>` tags are syntactically incorrect ([spec](http://www.atomenabled.org/developers/syndication/atom-format-spec.php#element.category)). With this patch it validates.

<pre>
Index: templates/atomitem.tmpl
===================================================================
--- templates/atomitem.tmpl     (revision 2640)
+++ templates/atomitem.tmpl     (working copy)
@@ -8,7 +8,7 @@
        <link href="<TMPL_VAR PERMALINK>"/>
        <TMPL_IF NAME="CATEGORIES">
        <TMPL_LOOP NAME="CATEGORIES">
-       <category><TMPL_VAR CATEGORY></category>
+       <category term="<TMPL_VAR CATEGORY>" />
        </TMPL_LOOP>
        </TMPL_IF>
        <updated><TMPL_VAR DATE_3339></updated>
</pre>