cleanup makefile and stuff
set up code that should load an img into halide's favorite data structure
stubbed out gradient computation
what does 'Error: p0 is accessed beyond the extent in dimension 0' mean? I was guessing it was an artifact of not clamping, but adding clamping didn't help.
aha, the clamp() code that I copy/pasted off the internet had an off-by-one. fixed.