Experimentation to fix Sersic profile precision (match GalFit in central pixels) by modifying integration scheme.
Add a fix-up contribution to Sersic pixel values based on the per-pixel gradient (better estimates the "average" surface brightness per pixel). Fractional errors with respect to GalFit are now on order of 1-2% in the central 4 pixels, and even less elsewhere.
Merge pull request #4 from mmechtley/bug/sersic-integration

Bug/sersic integration