title: Rails: How to add an empty 'required' attribute to a radio_button_tag
body: <p>I'm trying to use a <code>radio_button_tag</code> to generate a radio-button tag like:</p>
  
  <pre><code>&lt;input type="radio" ... required&gt;
  </code></pre>
  
  <p>in order to add form validation (I'm using Foundation and trying to make use of the Abide library). The closest I can get is:</p>
  
  <pre><code>radio_button_tag 'my_radio', ... , required: ''
  
  # =&gt; &lt;input type="radio" ... required="required"&gt;
  </code></pre>
  
  <p>This seems to be good enough for Abide to work, but is there a way I can get what I want out of the Rails helper? I've tried <code>required: true</code> in place of <code>required: ''</code> but it behaves the same.</p>