New closeOnWindowScroll option. Various bugfixes.

Hello, nice timepicker.

I noticed that when scrolling the timepicker list using the mousewheel until the end, the timepicker closed. The reason was that once the list cannot scroll anymore, wheel events cause the closest scrollable parent to scroll. I recently examined this "scroll wheel bubbling" problem and found no satisfying solution to prevent it.

So I just added an option disable closing on window scroll. I would have just completely removed this behaviour, but I assumed that it was there because someone needed it, so I added an option instead.

The pull request also include some small no-brainer bugfixes.

Regarding the position/offset fix not working when there are margins on body: don't put margins on body. It breaks a common jquery coding pattern and it does not make sense anyway.

Regards.

PS: I also completely rewrote datepair as jquery ui plugin, but it's not on github yet. Would you be interested?