Revert changes to setup.py
    
    07c45043b34d1b967d15490ae072f79772bff767 converts from distutils to
    setuptools, but it seems the latest setuptools doesn't read MANIFEST
    causing the build to fail (and also is missing a lot of files in
    `test/`).
    
    Temporarily revert it. We should probably rewrite to use a declarative
    format at some point anyway.
    
    Signed-off-by: Michel Alexandre Salim <salimma@fedoraproject.org>