BUG: GEE score

Fixes a bug in GEE score test that crept in somewhere during refactoring.  There was previously no test coverage for GEE score testing.  I added a simple regression test here.
same but better is `assert_allclose(wald_p, score_p, atol=0.02)`
(more informative failure message, and assert get optimized away in byte compiling python code with option -o)