sys-bio/roadrunner: v2.9.1

This release significantly increases support for named stoichiometries: Stoichiometries with names (i.e. 'n') can now be set with 'rr.n = 2', etc. Steady state works with changed stoichiometries. Roadrunner now notices when named stoichiometries are the target of assignment rules or rate rules, and correctly refuses to simulate those models (it was ignoring them and claiming to simulate anyway, before). You can set stoichiometries directly with 'stoich(species, rxn)'