v0.4.0

This release introduce a minor backward incompatibility by moving the headers files.

• Move the header files from tsl to include/tsl for more coherence with other C++ libraries.
• For CMake users, add an exported target tsl::robin_map to be used with target_link_libraries.
• Fix issue #6 by circumverting a bug in MSVC on insert when using a pointer as type in a set. The bug resulted in an infinite recursion inside the insert function. (#7)