Improve catboost unit test (#364)
Improve catboost unit test (#364)

* Make catboost test more robust to change in catboost performance.
* Improve catboost test.

maartenbreddels/vaex,maartenbreddels/vaex,maartenbreddels/vaex,maartenbreddels/vaex,maartenbreddels/vaex,maartenbreddels/vaex