title: Add class to collection_select on Ruby On Rails formulary
body: <p>I'm using a form for create a record in RoR. I've dropdown menu and I don't know how to add a class for styling this element.</p>
  
  <p>Code:</p>
  
  <pre><code>&lt;%= f.collection_select :id, TipusProducte.order(:nom),:id ,:nom, include_blank: false, class: "btn btn-secondary dropdown-toggle" %&gt;
  </code></pre>
  
  <p>But this class doesn't work, this style is from Bootstrap.</p>
  
  <p>Thanks!</p>