Adds some more checks to prevent segfaults with faulty data. Added a `repair` function that can repair some invalid polygons returned after set operations.
0.1.3
FIX: Workaround for a CGAL bug that could lead to segfaults during computing the difference of polygons (this bug should be fixed in later releases of CGAL, too).
0.1.1
Trying to fix long_description error of PyPI release. No idea, why it is complaining.