Revert "Relative links for everything"

This reverts commit ff484f854e.

templates/categories.html

@@ -6,7 +6,7 @@
     <h1>Categories on {{ SITENAME }}</h1>
     <ul>
     {% for category, articles in categories|sort %}
-        <li><a href="./{{ category.url }}">{{ category }}</a> ({{ articles|count }})</li>
+        <li><a href="{{ SITEURL }}/{{ category.url }}">{{ category }}</a> ({{ articles|count }})</li>
     {% endfor %}
     </ul>
 {% endblock %}