setup: fix failing pip installation

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>
setup: subprocess.check_output rather than commands.getoutput

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>
Bump version to 0.2.3

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>