%cargo_install is now smart to handle libs and bins
    
    So far we had %cargo_install (for binaries) and %cargo_install_crate
    (for libraries) which is a bit awkward and requires us to put
    additional arguments for latter one.
    
    We can do all the magic behind the scene.
    
    Closes: https://pagure.io/fedora-rust/rust2rpm/issue/7
    Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>