fixed rss content and added header information to rss link

app/views/layouts/application.html.slim

@@ -5,6 +5,7 @@ html
     = stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track' => true
     = javascript_include_tag 'vendor/modernizr'
     = csrf_meta_tags
+    = auto_discovery_link_tag(:rss, params.merge(format: :rss))
 
   body
     .row

app/views/search/index.rss.builder

@@ -8,7 +8,7 @@ xml.rss :version => "2.0" do
     @papers.each do |doc|
       xml.item do
         xml.title doc.name
-        xml.description article.content[0, doc.content.length < 30 ? doc.content.length : 30]
+        xml.description truncate(doc.content, length: 768)
         xml.pubDate doc.published_at.to_date.to_s(:rfc822)
         xml.link doc.url
         xml.guid doc.url