Adjust the ffmpeg webm command line

Update the audio bit rate/quality option for newer ffmpeg.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>
Add the ability to run a program after each file encoding

Add an optional -e argument that takes a full path to a program/script
that will called with the name of the newly encoded file as argv[1]
after each file is encoded.

This would be useful if some post processing of the file is required.

Signed-off-by: Andrew Clayton <andrew@digital-domain.net>