made the test robust to some floating point errors
made the test robust to some floating point errors

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