TST: more changes like self.assertTrue(x == y, message) -> assert_equal(x, y)

More boring changes.
I couldn't find this used anywhere else in scipy except in one comment https://github.com/scipy/scipy/pull/3945#discussion_r17213789.  Also when I search https://github.com/scipy/scipy/search?q=nose it looks like most direct uses of `nose` should be replaced by `numpy.testing`?  I've used `assert_array_less` from numpy.testing in situations like this before, and I think it works OK even though the arguments are not arrays, so maybe I'll use that instead.