added test for wrong file format type to test_hashbits
added test for wrong file format type to test_hashbits

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