updated sandbox README with calc-error-profile
updated sandbox README with calc-error-profile

jas14/khmer,kdmurray91/khmer,ged-lab/khmer,ged-lab/khmer,ged-lab/khmer,Winterflower/khmer,Winterflower/khmer,F1000Research/khmer,F1000Research/khmer,souravsingh/khmer,souravsingh/khmer,F1000Research/khmer,souravsingh/khmer,jas14/khmer,Winterflower/khmer,jas14/khmer,kdmurray91/khmer,kdmurray91/khmer