add twine for PyPI releases
add twine for PyPI releases

ricardogsilva/pycsw,ricardogsilva/pycsw,bukun/pycsw,geopython/pycsw,bukun/pycsw,tomkralidis/pycsw,kalxas/pycsw,kalxas/pycsw,bukun/pycsw,tomkralidis/pycsw,ricardogsilva/pycsw,geopython/pycsw,tomkralidis/pycsw,kalxas/pycsw,geopython/pycsw