Remove references to UTC

I was getting some odd behaviour when using the dev branch (as at 7a5f638) where the calendar was showing dates offset by -1 day, although picking them resulted in the correct date filling the input. To illustrate, Wednesday 21 October 2014 was showing up - impossible date - but clicking it filled the input with 22 October.

I just removed all references to UTC in picker.date.js and it seems to behave itself.