adding readme to core
adding readme to core


Former-commit-id: 6bbdfcc15d3f74377a281b6b566304690f38ff32 [formerly fb8a26601eb3877d74807448257f7122322834b8]
Former-commit-id: 75889a1ff2404e79fa22c55fa2ea5e848af25b77
andrewplummer/Sugar,romancow/Sugar,romancow/Sugar,andrewplummer/Sugar