add guess_z option to fit_lc()
add guess_z option to fit_lc()

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