feature:Implement the load bar at the top of the page

see [demo](http://shenzekun.cn/)
use [pace.js](http://github.hubspot.com/pace/docs/welcome/)
just  add two sentences

layout/_partials/head.swig

@@ -2,6 +2,9 @@
 <meta http-equiv="X-UA-Compatible" content="IE=edge" />
 <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1"/>
 
+<script src="//cdn.bootcss.com/pace/1.0.2/pace.min.js"></script>
+<link href="//cdn.bootcss.com/pace/1.0.2/themes/blue/pace-theme-flash.min.css" rel="stylesheet">
+
 
 {% if theme.han %}
   {% set Han_uri = url_for(theme.vendors._internal + '/Han/dist/han.min.css?v=3.3') %}