title: selectize.js add option dynamically with class attribute
body: <p>I am trying to dynamically add an option to the select dropdown
  I use the following code:</p>
  
  <pre><code>selectize.addOption({value:tuples[key].label,text:value});
  </code></pre>
  
  <p>However now I also <strong>want to add a class attribute</strong> to the option tag.</p>
  
  <p>I tried the following:</p>
  
  <pre><code>selectize.addOption({value:tuples[key].label,text:value,'class':'subdivide'});
  </code></pre>
  
  <p>However it does not add the class "subdivide" to the option
  Could anybody suggest how can I add the class attribute to the option tag when adding the option.</p>