clarify Makefile targets; tweak autopep8 to ignore E309
clarify Makefile targets; tweak autopep8 to ignore E309

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