Added basic setup.py.

tree2ogg can now be installed using pip.
Add logging support.
Move script functionality into a class.

Make the script more organized.
Determine default number of jobs in SubprocessPool.

This functionality should be part of SuprocessPool and not the main
script.
Add support to copy playlists.

Also refactored the code to make it more maintainable.
Add option to pass arguments to oggenc.