Merge pull request #433 from jorisv/topic/add_std_unique_ptr

.github/workflows/macos-linux-conda.yml

.github/workflows/windows-conda.yml

CHANGELOG.md

CMakeLists.txt

include/eigenpy/eigenpy.hpp

include/eigenpy/std-unique-ptr.hpp

include/eigenpy/ufunc.hpp

include/eigenpy/utils/python-compat.hpp

include/eigenpy/utils/traits.hpp

include/eigenpy/variant.hpp

unittest/CMakeLists.txt

unittest/python/test_std_unique_ptr.py

unittest/python/test_variant.py.in

unittest/std_unique_ptr.cpp

unittest/variant.cpp.in