title: fullcalendar custom end date
body: <p>Is it possible to create a custom end date, based on a choice from a selectbox?
  Let say I have this HTML - It has a title, and a duration of an event:</p>
  
  <pre><code>&lt;select name="event-title" id="event-title"&gt;
    &lt;option value="Træning" data-duration="01:00"&gt;Træning&lt;/option&gt;
    &lt;option value="Træning + Måling" data-duration="01:15"&gt;Træning og måling&lt;/option&gt;
    &lt;option value="Billeder" data-duration="00:20"&gt;Foto Session&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>When clicking add event, then the end date/time, should be the day and starttime clicked + the duration:</p>
  
  <p>See code here with comments:</p>
  
  <pre><code>select: function (start, end, allDay) {
    $('#fc_create').click(); //trigger modal
    var startHours = moment(start).format('hh:mm'),
        started = start,
        ended = end;
  
    //started variable could return: Mon Jan 11 2016 09:10:00 GMT+0000
  
    //Set value to selected time
    $("#event-start").val(startHours);
  
    $(".antosubmit").on("click", function () {
      var title = $("#event-title").val(),
          duration = $("#event-title").find("option:selected").data('duration');
  
      if (end) {
        //Returns ex: Mon Jan 11 2016 09:35:00 GMT+0000
        // However, the end time here should be the starttime + the duration - So in this it should be: 10.10
        // as the start time was 09:10 + a duration on 1 hour (from the selectbox)
        ended = end 
      }
  
      if (title) {
        calendar.fullCalendar('renderEvent', {
          title: title,
          start: started,
          end: end,
          allDay: false
        },
        true); // make the event "stick"
      }
      $('#title').val('');
      calendar.fullCalendar('unselect');
  
      $('.antoclose').click();
  
      return false;
    });
  }
  </code></pre>