"Until time" input

Hey guys, thanks for this awesome tool, it really has taken a lot of the headache out of managing recurring events. I had to make use IceCube::Rule's until/until_time feature recently, so I added this functionality to the recurring_select. It accepts a configuration parameter for the date format, and to make things easier I added jQuery UI (datepicker only) as a dependency, but I would be happy to switch to using Chronic or some other simpler gem to handle the date format/parsing. Let me know if you'd like to include this and what direction (if any) you'd like to go with the dependencies so I can update the documentation as well!