Better handling of default value for arguments.

Changed the config file format : the name of the section is now "magnatune" instead of "default". Remember to update your config files !
Updated to python 3.3.
Simplified the update checking code
Changed the way the config file is found (also moved it).
Switched to requests
Switched to the sqlite dump, using sqlalchemy.

This makes everything much faster than reading a 70 megs xml file.
Completely removed lxml
Fixed the tests, after all that changes

Well, deleted most of it, but I really don't liked the overmocking in
there.
Removed the extra logging from requests