Update README.md
Added DifferentialFVA back into the codebase
optlang is not used explicitly anymore in OptlangBasedModel

Setting an objective will use model.solver.interface.Objective now to check if it is a valid Objective or to create a new objective
OptlangBasedModel -> SolverBasedModel
bpcy -> biomass_product_coupled_yield; no more absolute paths
Using Ali's wheelhouse at https://pypi.drosophi.la --no-index for python-libsbml-experimental
scipy is already in requirements.txt (double requirement issue on travis-ci)
Added travis-ci badge
Updated README.md
Updated requirements.txt
Updated requirements.txt
Updated requirements.txt
Trigger travis-ci
Skipping MultiprocessingView tests if not available
Merge branch 'devel' into joao

Conflicts:
	tests/test_heuristics.py