This change is somewhat related to #1604 .
* Catch is now at v2.3.0
* Eigen is now at v3.3.5
* FindMathemaica is now at v3.2.4
* fmtlib (formerly cppformat) is now at v4.1.0 (v5.x.x is not compatible with our code).
* msgpack-c is now at v3.0.1
* pybind11 is now at v2.2.3
* All the other submodules have been moved to the latest master commit
* All submodules are sorted alphabetically