[CLEANUP] Make copyCssWithMediaToStyleNode private
[CLEANUP] Make copyCssWithMediaToStyleNode private

Fixes #216

Synchro/emogrifier,jjriv/emogrifier,MyIntervals/emogrifier,ernsto/emogrifier,OzzyCzech/emogrifier,sanderkruger/emogrifier,Seldaek/emogrifier,ricardofiorani/emogrifier