bring docstrings in nest.py up to date
bring docstrings in nest.py up to date

kbarbary/sncosmo,sncosmo/sncosmo,sncosmo/sncosmo,sncosmo/sncosmo,kbarbary/sncosmo,dannygoldstein/sncosmo,dannygoldstein/sncosmo,kbarbary/sncosmo,dannygoldstein/sncosmo