add support for ffmpeg/ffprobe version 2.2.2

built and tested on mac os x 10.9.2 with ruby 2.1.1 

ffprobe related commits:
http://git.videolan.org/?p=ffmpeg.git;a=commit;h=fe87a40de6792ee97686ce4a215268041e3fcf81
http://git.videolan.org/?p=ffmpeg.git;a=commit;h=14404170b95913e80555416f921e78c58f3ffff0