fix docs; rotation is ccw
reorganization, optimization, parallelization, blur, sharpen
blur radius = 3 * sigma: slower but more precise
positive sigma check fix
Clone fast path added for *image.Paletted
better err msg
two new functions: Invert, Grayscale
gamma, contrast, brightness adjustments
fix comment
update readme
contrast calculation bug fixed
no need to fill a new image with zeros
New: width and height - check positive
AdjustSigmoid function added
math import
upd readme
TIFF and BMP image format support added. Now Mercurial is needed to 'go get' the package