Use CMAKE_CXX_FLAGS so that linker gets the right flags.
Enable glewExperimental for MacOS X due to misreported extensions.
Open glfw window using forward compatible OpenGL 3 context.
Fix building with non-X11 OpenGL on MacOS X.
Update README.rst to reflect MacOS X support.
Force MacOS X to use OpenGL 3.2; thats the maximum it currently supports.
012_checker_sphere updated to be compatible with MacOS X.

Using index buffer objects as MacOS X does not support index arrays
being passed directly to glDrawElements (OpenGL implementation bug?).