TST: distance: nose.tools.assert_true -> numpy.testing.assert_
TST: distance: self.assertRaises -> numpy.testing.assert_raises
TST: cdist: self.assertTrue(within_tol()) -> _assert_within_tol()
TST: pdist: self.assertTrue(within_tol()) -> _assert_within_tol()
TST: distance: self.assertTrue(x == y) -> assert_equal(x, y)
Merge pull request #4330 from argriffing/update-distance-tests

MAINT: update distance tests to use numpy.testing & DRY