Add additional bold variant of the Ubuntu font family

This allows us to have bold headers at smaller font sizes.

ckan/templates/layout_base.html

@@ -27,7 +27,7 @@
   <link rel="alternate" type="application/atom+xml" title="${g.site_title} - Recent Revision History" href="${h.url_for(controller='revision', action='list', format='atom', days=1)}" />
   </py:otherwise>
   </py:choose>
-  <link href='http://fonts.googleapis.com/css?family=Ubuntu' rel='stylesheet' type='text/css' />
+  <link href='http://fonts.googleapis.com/css?family=Ubuntu:400,700' rel='stylesheet' type='text/css' />
 
   <link rel="stylesheet" href="${h.url_for_static('/scripts/vendor/jqueryui/1.8.14/css/jquery-ui.custom.css')}" type="text/css" media="screen, print" />
   <link rel="stylesheet" href="${h.url_for_static('/css/bootstrap.min.css')}" type="text/css" media="screen, projection" />