title: Creating an item if not already exists in Selectize.js select box and ajax update the new added item
body: <p>I was using <a href="https://github.com/brianreavis/selectize.js">Selectize.js</a> in a select box, What i need is, if an item is not in the list of options i would need to add a new item. When new item is added, i want to have an ajax call to update the newly added item to my database.</p>
  
  <p>In their <a href="https://github.com/brianreavis/selectize.js/blob/master/docs/usage.md">documentiation</a>, it says that we can use "create" to have the selectize to add an item. </p>
  
  <blockquote>
    <p>create - Allows the user to create a new items that aren't in the list of options. This option can be any of the following: "true" (default behavior), "false" (disabled), or a function that accepts two arguments: "input" and "callback". The callback should be invoked with the final data for the option.</p>
  </blockquote>
  
  <p>But i am not able to understand how to use the call back here. can anyone help?</p>
  
  <p>The following is an example of my content, the values are ids of the items in the db. I would like to have the new item added to db and returned with the value as id from db and populate and get selected in the select box.</p>
  
  <pre><code>&lt;select name="fruits" id="fruits" placeholder="Select a fruit" &gt;
      &lt;option value="1"&gt;Apple&lt;/option&gt;
      &lt;option value="2"&gt;Orange&lt;/option&gt;
      &lt;option value="3"&gt;Mango&lt;/option&gt;
      &lt;option value="4"&gt;Grape&lt;/option&gt;
  &lt;/select&gt;
  
  &lt;script&gt;
      $(function(){
          $('#fruits').selectize({
              create:function (input, callback){
  
             }
          });
      });
  &lt;/script&gt;
  </code></pre>