title: Select2 open dropdown on focus
body: <p>I have a form with multiple text inputs and some select2 elements. 
  Using the keyboard to tab between fields works fine - the Select2 element behaves like a form element and receives focus when tabbing.
  I was wondering if it is possible to open the dropdown when the Select2 element gets focus.</p>
  
  <p>Here's what I've tried so far:</p>
  
  <pre><code>$("#myid").select2().on('select2-focus', function(){
       $(this).select2('open');
  });
  </code></pre>
  
  <p>But using this code makes the dropdown to open again after a selection is made. </p>