fix the album art.

Requires MP3v2 version 2.
There is a bug in 1.9.1 that prevents pictures from
getting set.
https://code.google.com/p/mp4v2/source/detail?r=394&path=/trunk/util/mp4tags.cpp
add an mp4v2 version check.
remove some debug messages.
don't install homebrew version of mp4v2.