TST: add failing test, bug #1221
REF/ENH: add `_init_keys` to recreate model closes #1221 closes #1609
TST: change smoke test results negbin geometric llnull
TST: TestProbitCG.test_conf_int use relative error (intermittend test failure)
REF: add _get_init_kwds  overwrite in CountModel
Merge pull request #1610 from josef-pkt/clone_fix_llnull

BUG/ENH fix llnull, extra kwds to recreate model