py3 compat in doc helpers
py3 compat in doc helpers

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