make fitted nh3 models inherit modelkwargs
make fitted nh3 models inherit modelkwargs

allisony/pyspeckit,e-koch/pyspeckit,pyspeckit/pyspeckit,pyspeckit/pyspeckit,low-sky/pyspeckit,e-koch/pyspeckit,keflavich/pyspeckit,low-sky/pyspeckit,keflavich/pyspeckit,jpinedaf/pyspeckit,allisony/pyspeckit,jpinedaf/pyspeckit,vlas-sokolov/pyspeckit,vlas-sokolov/pyspeckit