Datepicker usability

[jrubenoff]

A few usability issues with the datepicker I'm having trouble implementing myself:

1. The default time on the datepicker should be 12:00am, not the current time.

2. The datepicker input fields should have placeholders, so that disabled users understand the format in which they should type:

[ajb]

Added the placeholder.

As for the default time, I'm not sure it's a supported option. I opened a ticket that we can track: bevacqua/rome#164

[qmarcos]

I have answered on issue #164 issue right now. You can do it calling setValue method on the instance that rome initialization returns.