title: How to allow user to select empty string on Select2
body: <p>The texbox is dynamically filled with a remote call using Select2 and I want to allow users  to leave the field blank. </p>
  
  <pre><code>$("#e6").select2({
      placeholder: "Search for a movie",
      minimumInputLength: 1,
      ajax: { 
          url: "http://api.rottentomatoes.com/api/public/v1.0/movies.json",
          dataType: 'jsonp',
          data: function (term, page) {
              return {
                  q: term, // search term
                  page_limit: 10,
                };
          },
          results: function (data, page) { 
              return {results: data.movies};
          }
      },
   });
  </code></pre>
  
  <p>Here is working example <a href="http://ivaynberg.github.io/select2/index.html#ajax" rel="noreferrer">http://ivaynberg.github.io/select2/index.html#ajax</a></p>