Hide scrollbars while capturing

I was getting some ugly horizontal scrollbars on captured images (on Guardian.co.uk pages) and wondered if it might make sense to just disable scrollbars entirely during the capture and restore them later.

This fixes the problem I was having and seems to work on the other (handful of) sites I've tested.

I also reduced the pause between captures to 100ms (from 1s) because it seems there is now less need to pause - maybe this is too aggressive, though. I did this based on the (now-altered) comment that mentioned pausing to allow for scrollbars to be displayed. Not pausing at all doesn't work, at least on some pages, so I reduced the value and the sites I've tried are ok.  BUT... I have a fast laptop, so the 100ms value might need to be upped again.