Add "next" link to Atom feeds

app/helpers/atom_builder_helper.rb

@@ -90,6 +90,10 @@ module AtomBuilderHelper
     xml.link(rel: 'self', type: 'application/atom+xml', href: url)
   end
 
+  def link_next(xml, url)
+    xml.link(rel: 'next', type: 'application/atom+xml', href: url)
+  end
+
   def link_hub(xml, url)
     xml.link(rel: 'hub', href: url)
   end

app/views/accounts/show.atom.ruby

@@ -14,6 +14,7 @@ Nokogiri::XML::Builder.new do |xml|
 
     link_alternate xml, TagManager.instance.url_for(@account)
     link_self      xml, account_url(@account, format: 'atom')
+    link_next      xml, account_url(@account, format: 'atom', max_id: @entries.last.id) if @entries.size == 20
     link_hub       xml, api_push_url
     link_salmon    xml, api_salmon_url(@account.id)