Add background for two-finger swipe animation in OS X
Add background for two-finger swipe animation in OS X

See https://gist.github.com/louischan/b478ed027ab1cd6d785f for method
to enable this effect

louischan/simplewhite,johngraciliano/simplewhite,SW1FT/simplewhite,gabriel-cliqz/simplewhite,3marcusw/simplewhitecompact,3marcusw/simplewhite