Update Stylus to 0.43

* 0.43.1 (not 0.43.0) because latter had an [issue with Nib](https://github.com/LearnBoost/stylus/issues/1457) that was fixed in 0.43.1.
* `compress` behavior [was changed](https://github.com/LearnBoost/stylus/commit/42d81d795ebbd759b313d38f83a849dea7434442).