Fix urls in the theme

Copied from how themes in pelican-themes do it.

test-theme/templates/base.html

@@ -21,7 +21,7 @@
 	{# TODO: More meta tags #}
 
 	{# CSS and other: #}
-	<link rel=stylesheet href="{{ THEME_STATIC_DIR }}/css/theme.css">
+	<link rel=stylesheet href="{{ SITEURL }}/{{ THEME_STATIC_DIR }}/css/theme.css">
 
 	{# Title setting #}
 	{% if page_title %}

test-theme/templates/sidebar.html

@@ -6,14 +6,14 @@
 	<h2>Categories</h2>
 	<ul>
 	{% for category, _art in categories %}
-	<li><a href="{{ category.url }}">{{ category }}</a></li>
+	<li><a href="{{ SITEURL }}/{{ category.url }}">{{ category }}</a></li>
 	{% endfor %}
 	</ul>
 
 	<h2>Tags</h2>
 	<ul>
 	{% for tag, _art in tags %}
-	<li><a href="{{ tag.url }}">{{ tag }}</a></li>
+	<li><a href="{{ SITEURL }}/{{ tag.url }}">{{ tag }}</a></li>
 	{% endfor %}
 	</ul>
 </div>