Old blur handler isn't removed removed when datepicker options change.

The issue is evident here:

http://plnkr.co/edit/xVPSbgKDjrbNc6g4XiZN?p=preview

if you change the date in the first datepicker, the second one becomes completely non-functional in Chrome and somewhat broken in Firefox (you have to click twice to get the value to change and get an '$apply already in progress exception')