Desired end-state: python scripts generate both python and MATLAB wrappers. Because there is an API change in python, this will bump our version to 4.1.

• PR 0 to package existing cython wrapper for manylinux, README, so loads from colab (this is done in a separate repo, https://github.com/borglab/gtsam-manylinux-build)
• Add pybind to feature/new_wrapper
• Add pybind wrapper version (purely additive, duplicates all python scripts/tests into gtsam_py, includes GTSAM changes), fix Values (done), PR to feature/new_wrapper
• Add travis CI for cython wrapper, PR to develop
• Add travis CI for new wrapper, PR to feature/new_wrapper
• Do PR to develop with new wrapper and we ask everyone to test/switch
• @ProfFan tests MATLAB wrapper
• Switch MATLAB wrapper to be created by python, includes Matthew unit tests, PR to feature/new_wrapper
• Fix most Bugs before 4.1
• Remove cython wrapper and old c++ wrap, PR to develop (only file deletions)
• Create release branch and do PR to master, add release tag
• Create packaging in gtsam-manylinux-build for 4.1 so we can pip install, think about versioning