Added cmake option BUILD_TESTS
Added cmake option BUILD_TESTS

Sometimes one might want to build the library
without running and building the tests.
So, here is an cmake option for that. BUILD_TESTS.
It's default on.

assaabloy-ppi/binson-c-light,assaabloy-ppi/binson-c-light,assaabloy-ppi/binson-c-light