Updated procedure for evaluating species and characteristic fluxes.
Updated procedure for evaluating species and characteristic fluxes.

The new procedure only requires one call to getReactionRates() per iteration,
rather than two, which should speed things up significantly.

This also fixes a bug wherein only the core species were having their relative
fluxes evaluated.

pierrelb/RMG-Py,chatelak/RMG-Py,comocheng/RMG-Py,KEHANG/RMG-Py,nyee/RMG-Py,nyee/RMG-Py,enochd/RMG-Py,faribas/RMG-Py,pierrelb/RMG-Py,enochd/RMG-Py,KEHANG/RMG-Py,chatelak/RMG-Py,comocheng/RMG-Py,faribas/RMG-Py,nickvandewiele/RMG-Py,nickvandewiele/RMG-Py