make the fit type configurable in the ammonia fitting wrapper
make the fit type configurable in the ammonia fitting wrapper

low-sky/pyspeckit,jpinedaf/pyspeckit,pyspeckit/pyspeckit,low-sky/pyspeckit,keflavich/pyspeckit,e-koch/pyspeckit,keflavich/pyspeckit,jpinedaf/pyspeckit,pyspeckit/pyspeckit,e-koch/pyspeckit