Log Message:
py-cairo: update to 1.17.0.

1.17.0 - 2018-04-15
-------------------

* :class:`cairo.Surface` and :class:`cairo.Device` can now be used as context
  managers. :bug:`103`
* Fix a leak when a cairo error was raised.
* Fix a leak when a mapped surface was GCed instead of unmapped.
* Make it possible to use the C API with Python 3 outside of the compilation
  unit doing the import by defining ``PYCAIRO_NO_IMPORT``. :bug:`110`
* Implement PEP 561 (added a py.typed marker)