title: bootstrap-datepicker empties field after selecting current date
body: <p>If I have autoclose enabled, and I select the field from the calendar that is already chosen, it empties the field and then closes the datepicker as expected. How can I still have the autoclose feature, but not have it empty the field?</p>
  
  <p>Look at the demo for an example, <a href="http://eternicode.github.io/bootstrap-datepicker/?markup=input&amp;format=&amp;weekStart=&amp;startDate=&amp;endDate=&amp;startView=0&amp;minViewMode=0&amp;todayBtn=false&amp;language=en&amp;orientation=auto&amp;multidate=&amp;multidateSeparator=&amp;autoclose=on&amp;keyboardNavigation=on&amp;forceParse=on#sandbox" rel="noreferrer">http://eternicode.github.io/bootstrap-datepicker/?markup=input&amp;format=&amp;weekStart=&amp;startDate=&amp;endDate=&amp;startView=0&amp;minViewMode=0&amp;todayBtn=false&amp;language=en&amp;orientation=auto&amp;multidate=&amp;multidateSeparator=&amp;autoclose=on&amp;keyboardNavigation=on&amp;forceParse=on#sandbox</a></p>
  
  <ol>
  <li>Make sure autoclose is on</li>
  <li>Select a date.</li>
  <li>open the datepicker again, select the currently selected date again.</li>
  <li>field is empty again</li>
  </ol>
  
  <p>Thanks</p>