updated bioreactor classes
updated bioreactor class
updated ex_dfba
Merge branch 'master' into kai-branch
added Batch and IdealFedbatch classes to bioreactor module
added a new dfba example
debugged bioreactor module
cosmetic changes to ex_dfba2
cleaning up examples directory
clean_bigg_ids() now removes trailing "_" in sbml files
Merge branch 'kai-branch'

Conflicts:
	examples/ex_dfba2.py