Corrected test for empty compartment lists in function write_cobra_model_to_sbml_file to allow default compartment lists to be generated when not specified
Grouped together code & comments that deal with compartments in function write_cobra_model_to_sbml_file
Merge pull request #60 from afif-elghraoui/master

Minor Bug Fix in write_cobra_model_to_sbml_file to Allow Default Compartments to be created