* Add function_ref
Made by the same guy that made the expected package, maybe we should name them tl_expected and tl_function_ref as they're common names
* function_ref: use C++14 for tests
* Mark expected and function_ref headeronly
* Mark catch2, hopscotch-map and sol2 as header-only
* Update sol2 to v3.2.3 (fixes compilation error)
* Add tl_ prefix to expected and tl_function_ref packages