Improve exception safety with smart pointers

Would you like to [wrap any pointer data members](https://github.com/pitzer/SiftGPU/blob/b46bd5b8cc5cfdc1dc163444b72c705569800b6d/src/SiftGPU/PyramidCL.cpp#L50 "Update candidate: PyramidCL class") with the class template “[std::unique_ptr](https://en.wikipedia.org/wiki/Smart_pointer#unique_ptr "Description for the usage of smart pointers")”?