Ensure we've got a good Datepicker solution baked in

[lorennorman]

Figure out what's up with Datepickers these days (the Material one we used to use broke at some point, may still be broken.)

• Pick a Datepicker and build it in
• Test the Datepicker to make sure dates are going in and coming out correctly
• Add a demo of it to the Kitchen Sink that shows the ideal way of using it

Do this in tandem with #18