Added Flux Balance Analysis (v 0.3.3)

setup.py

xbanalysis/_version.py

xbanalysis/model/fbc_objective.py

xbanalysis/model/xba_model.py

xbanalysis/model/xba_reaction.py

xbanalysis/model/xba_species.py

xbanalysis/problems/__init__.py

xbanalysis/problems/fba_problem.py

xbanalysis/problems/gba_problem.py

xbanalysis/problems/lp_problem.py

xbanalysis/utils/utils.py