Add Apple CI

See merge request !3

Use C++ compiler throughout on macOS (to avoid C compilers crying about -std=c++14) (reported by Kip Hart)

Add Pytest/JUnit/Gitlab integration

See merge request !2

Port to pybind11

See merge request !1

fix in setup for python3, is backward compatible to python2

Fix segfaults on win-amd64

Use size_t instead of unsigned long to handle pointers.