title: Clicking calendar button not working on Angular UI datepicker inside accordion
body: <p>Here is a plunker <a href="http://plnkr.co/edit/2Fs6vCciXRRc7GeUwyR2?p=preview" rel="nofollow">http://plnkr.co/edit/2Fs6vCciXRRc7GeUwyR2?p=preview</a> </p>
  
  <p>Is anyone could help to advise why the calendar button is not working?
  However clicking the calendar textbox showing calendarpopup just fine.</p>
  
  <p>It seems that scope.$watch('isOpen', function(value) { ... }
  not working anymore when datepicker is inside accordion and using calendar button.</p>
  
  <p>many thanks in advance,</p>
  
  <p>Ferry</p>