Changed GradientMixin's get_gradient() to get_fitness_and_gradient() and VectorGradientMixin's get_jacobian() to get_fitness_vector_and_jacobian() to match BingoCpp's inheritance structure. Also added testing for C++ implementations of GradientMixin and VectorGradientMixin.
Changed GradientMixin's get_gradient() to get_fitness_and_gradient() and VectorGradientMixin's get_jacobian() to get_fitness_vector_and_jacobian() to match BingoCpp's inheritance structure. Also added testing for C++ implementations of GradientMixin and VectorGradientMixin.