use hash table in dispatcher

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
change hash table threshold to 90%

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
implement kmer counting (kmer coverage distribution)

Link: https://github.com/GeneAssembly/biosal/issues/56
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
add help page for argonnite

Link: https://github.com/GeneAssembly/biosal/issues/230
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>