Add field 'rss2_sn' for importing

app/models/bulletin.rb

@@ -16,6 +16,7 @@ class Bulletin
   field :public, :type => Boolean, :default => true
   field :postdate , :type => DateTime, :default => Time.now
   field :deadline , :type => DateTime
+  field :rss2_sn
 
   field :email_id
   field :email_sent, :type => Boolean, :default => false