TST: more changes like self.assertTrue(x == y, message) -> assert_equal(x, y)
TST: assert_(x < y) -> assert_array_less(x, y)
TST: use numpy.testing in test_hierarchy.py
Merge pull request #4321 from argriffing/test-assertion-syntax-b

TST: more changes like self.assertTrue(x == y, message) -> assert_equal(x, y)
Merge pull request #4326 from argriffing/update-hierarchy-tests

TST: use numpy.testing in test_hierarchy.py