title: Rails - Simple Form - Not loading class option
body: <p>I'm having some troubles when I want to change the class of a form.
  I have this partial:</p>
  
  <pre><code>&lt;%= simple_form_for(@activity) do |f| %&gt;
  
      &lt;%= f.input :name %&gt;
      &lt;%= f.submit 'Guardar',:class=&gt;"btn success" %&gt;
  
  &lt;% end %&gt;
  </code></pre>
  
  <p>In the browser the form label has class="simple_form activity"</p>
  
  <p>According to Simple Form documentation, I can change the class by doing this</p>
  
  <pre><code>&lt;%= simple_form_for(@activity, :defaults=&gt;{:class=&gt;"my_class"}) do |f| %&gt;
  </code></pre>
  
  <p>But nothing is happening, what is wrong?</p>
  
  <p>JavierQ</p>