use routes to build graph

Link: https://github.com/GeneAssembly/biosal/issues/510
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
use assembly vertex

Link: https://github.com/GeneAssembly/biosal/issues/510
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>