add contig metrics tests
add contig metrics tests


Former-commit-id: cf4eeed462985994942bda0f1614865905f322e7
cboursnell/transrate,Blahah/transrate,roryk/transrate,cboursnell/transrate,cboursnell/transrate,roryk/transrate,Blahah/transrate,Blahah/transrate,roryk/transrate