Modified configuration.py. Fixed vdB03 quenching model. Fixed HOD_mock.

Still inching with baby steps towards a de-bugged HOD_Mock class. vdB03 is still poorly tested.
HOD_Mock still needs many minor modifications to flexibly work with all HOD types.

Configuration.py and read_nbody.py will need to be changed after Erik replies with
instructions for how to correctly use the astropy utils module.