use article url as disqus identifier

templates/mixins/disqus.jade

@@ -2,7 +2,7 @@ mixin disqus
   #disqus_thread
     script(type="text/javascript").
       var disqus_shortname = 'brettlangdon';
-      var disqus_identifier = '#{page.title}';
+      var disqus_identifier = 'http://brett.is#{page.url}';
       var disqus_title = '#{page.title}';
       var disqus_url = "http://brett.is#{page.url}";
       (function() {