Updated screencast to output three files

screencast will now output one video only file, one internal audio file
and one mic audio file now. I got rid of the presets for the moment, but
I might need to bring them back as recording/muxing and playing
minecraft at the same time will end up overheating my laptop. I don't
get to have all of my cores maxed at the same time it would seem (unless
I'm outside in the snow).