upgraded count-density script
updated count-density-by-position to use screed.open
added flush outfp
added various generated files
provided hashbits consume_fasta_with_reads_parser; test needed.
added test for load-graph.py -n
Merge branch 'hashbits_read_parser' into mbe
Merge remote-tracking branch 'ged/bleeding-edge'
Merge count-density-by-position cleanup code.
Merge branch 'mbe' of github.com:ctb/khmer into mbe