title: simple_form renders radio buttons incorrectly
body: <p>Using simple_form I render some radio buttons to select Gender on registration page.</p>
  
  <p>code:</p>
  
  <pre><code>        = f.input :gender,
                :collection =&gt; gender,
                :as =&gt; :radio_buttons,
                :item_wrapper_class =&gt; 'inline'
  </code></pre>
  
  <p>This gives output like:</p>
  
  <p><img src="https://i.stack.imgur.com/I7sSF.png" alt="enter image description here"></p>
  
  <p>Is there a way to make the first radio button be behind Male and the 2nd radio button behind Female?</p>