adds hourLeadingZero option

[nathany]

We want to display hours with a leading space instead of a leading zero.

This adds a hourLeadingZero option, which defaults to the existing behavior.

[nathany]

@kbwood Any interest in merging this?

[Boltyk]

+1 for this change
And maybe not the leading space - just without leading zero.
Got onchange event fired up because of this option missing, when _setValue check, for example, 02:14 vs 2:14 and treat it as a different value.