Configurable date formats

[darrena092]

Hi!

Might put in a PR for this if there's interest in it.

I'm using this in a project, and found myself needing to change the date formats, as we don't tend to use Y-m-d much here in the UK (at least, users don't generally like it). I did this by just overriding the getCarbonDateFormat function.

It might be nice if we had some functions like useDateFormat('d/m/Y') and useTimeFormat('H:i:00') etc to make this a bit more straightforward.