title: capturing enter key in select2
body: <p>I'm using <a href="http://ivaynberg.github.io/select2/" rel="noreferrer"><strong>select2</strong></a> to present an editable selectbox. When user writes a statement which does not appear in the <code>list(select2, data)</code>, I show a button to add this statement to the list. </p>
  
  <p>Forcing users to click the button seems to me a little bit frustration. Is it possible to capture enter key in select2? I want to make user able to add his/her new statements into the list just by pressing enter key.</p>