Allow custom CSS in default blog theme if user is Pro. Addresses #16.

blogs/templates/blogs/themes/default/base.html

@@ -21,6 +21,14 @@
         window.blog_post = true;
 {% endblock %}
 
+{% block css %}
+    {% if blog_user.profile.is_pro and custom_css %}
+        <style type="text/css">
+            {{ custom_css.code }}
+        </style>
+    {% endif %}
+{% endblock %}
+
 {% block header %}
     <header class="main">
         <div class="inner group">

templates/base.html

@@ -25,6 +25,8 @@
         <link rel="alternate" type="application/rss+xml" title="RSS" href="{{ request.path }}?rss{% if not public %}&amp;api_key={{ request.user.api_key.key }}{% endif %}" />
     {% endif %}
 
+    {% block css %}{% endblock %}
+
     <!--[if IE]>
         <style type="text/css">
             .group {