backwards compatibility with super()
backwards compatibility with super()

This changeset implements a call to `super` that is compatible both in
Python 2.7 with old-style classes and in current releases of Python
("new-style classes").  To learn more, read

1. https://docs.python.org/2.7/library/functions.html#super
2. https://docs.python.org/3.7/library/functions.html#super

tulip-control/tulip-control,tulip-control/tulip-control,tulip-control/tulip-control,tulip-control/tulip-control