Fixed OutOfMemoryError on OS X on large retina screens

When playing full screen on a Retina iMac, the 5120x2880 screenshots were taking too much memory and causing HearthStats Companion to fail with an OutOfMemoryError. The Companion was storing up to 20 images in a buffer for video, which is unnecessary for OS X that doesn't yet have video recording, so I've stopped it buffering when not recording a video. This fixes the OutOfMemoryError.
Fixes for deck export
- The positions of the cards on the deck screen had changed slightly in the G&G release, I have recalculated them and fixed them.
- Hearthstone no longer responds to the scroll wheel for scrolling through the deck. Switched to clicking on positions in the scrollbar instead.
Updated to version 0.21.1-SNAPSHOT