Provide CMake INTERFACE and INSTALL

[samaursa]

It would be nice to use the newer CMake INTERFACE option in conjunction with add_library and the appropriate install entries in the CMakeLists.txt.

It would also be nice to add the tests explicitly using add_test so that ctest can be run easily.

[MikeGitb]

It would be nice to use the newer CMake INTERFACE option in conjunction with add_library and the appropriate install entries in the CMakeLists.txt.

Please yes. It makes working with cmake and package management so much easier if all dependencies follow standard cmake best practices.

And once you do this: Please make #incluude <clara/clara.h> the default way to use it (just as with catch).