title: Builder options on Ruby Nokogiri :standalone
body: <p>I would like to to create XML that begins with:</p>
  
  <pre><code>&lt;?xml version = "1.0" encoding = "UTF-8" standalone ="no"?&gt;
  </code></pre>
  
  <p>But I cannot find how to add the '<code>standalone</code>' option in the Nokogiri documentation.</p>
  
  <p>My code is like this:</p>
  
  <pre><code>builder = Nokogiri::XML::Builder.new(:encoding =&gt; 'UTF-8', :standalone =&gt; 'no') do |xml|
  </code></pre>
  
  <p>But it fails when Nokogiri finds <code>:standalone</code>. The <code>:encoding</code> works.</p>