Ability to Start Calendar on Time Tab

[machineghost]

Sorry for filing so many tickets, but I have another feature that would be really handy. Right now there's no way to open the calendar on the time-picking tab. This is controlled by this.state.tab in input-moment, but that state isn't set from any prop.

If there was either a way to pass a tab prop, and have this used as the initial state, or have some other sort of mode="time", "showTime={true}", etc. that would be great. I could even file a pull request for it, if you just let me know which prop to use.

Thanks.

[aychtang]

This would be enabled by #78.