v3.1.0: Add C++ wrappers, CMake for C/C++, Python wrappers, and more …

…documentation.

v3.1.0 C/C++ headers only. Download this tag with --depth 1 to get th…

…e minimum files needed for using NVTX in C or C++ programs.

v3.0.1: Initial tag of NVTX v3 repo. Contains C API and doxygen-gener…

…ated docs.