Remove use of PyCXX in core C++ extensions
Change how array converter functions are defined
Add .clang-format to repository
Restore parallel testing
Documentation
Remove some obsolete TODOs
Fix compilation
Remove debugging prints
Fix curve simplification
Fix segfault on Python 3
More Python 3 fixes
Windows-related fixes, thanks to @cgohlke
Fix test_hexbin_pickable test
Fix Mac compile again
Remove usage of old Numpy API
Simplify read_png
Remove reference to PyCXX
Fix dimensions of greyscale image.
Merge pull request #3646 from mdboom/decxx-backend-agg

MNT : Remove PyCXX dependency for core extension modules