[Ur] New attempt to wrap a simple JS datepicker library (Pikaday) to use with Ur/Web

[Istvan Chung]

After hacking away at this for a couple hours, I think I've gotten it
(somewhat) working.  I've made a pull request to your GitHub repo.  If
you'd like me to explain the changes to you, I'm happy to do so off-list.

-- 
Istvan Chung