Added option to normalize by substrate uptake to plot flux envelope.
Small fix in MOMA.
Added __repr__ method to base classes (Gene, Metabolite, Reaction, Compartment).
Fix in transformation.simplify to also remove disconnected metabolites.
Some changes in combinatorial deletion method.
Fix in sbml wrapper to avoid creating empty KineticLaws (otherwise it doesn't pass the sbml validator test).
Fix in gurobi wrapper to avoid bug caused by calculating shadow price of disconnected metabolites.
Added greedy optimization method for rational strain design.
Added utility module to read and write tables as CSV files.
Changes in core unit tests.