[cpp]A numerical improvement. Refine tests.

[hungpham2511]

Changes in this PRs:

• Add randomized tests to compare Python and C++ API
• A minor fix to improve numerical stability.

Checklists:

• [x] Update CHANGELOG.md with a single line describing this PR

In progress: I will update this PR to run the integration test on CI.

[jmirabel]

Add randomized tests to compare Python and C++ API

Thanks. I was unsure how to put this test in the Python unit test.

[jmirabel]

I see that CI runs on xenial. On xenial, robotpkg provides Python 3.5 stuff, but not Python 3.6. So CI should install robotpkg-py35-pinocchio instead.

[jmirabel]

The available versions of py??-pinocchio depending on the distribution can be found here: http://robotpkg.openrobots.org/rbulk/robotpkg/math/py-pinocchio/index.html

[hungpham2511]

The available versions of py??-pinocchio depending on the distribution can be found here: http://robotpkg.openrobots.org/rbulk/robotpkg/math/py-pinocchio/index.html

Thanks. I am skipping the pinocchio tests for now, as on the base CI image is running 16.04 and there are only 2.7 and 3.5, which are incompatible with the python codebase.

[hungpham2511]

Look like we will need to upgrade the CI image to bionic and test with 3.6 and 2.7.

[jmirabel]

Another option is to install Pinocchio from conda. I never tried myself. https://github.com/conda-forge/pinocchio-feedstock