Add option to only catch intentionally raised exceptions

[moshimeow]

So there might be a simpler way to do this, but:

I have a dataset where I weed out bad samples through heuristics/geometry and explicitly raise an error when one of the checks doesn't pass. Then as I was hacking on it I got really confused before I realized "doh, Nonechucks is catching all my exceptions!"

So this is my solution: add an option where it'll only not raise an error if it gets a NoneChucksSkipException. This solution probably sucks, and if you want to reject it and say "no, do Y instead" I'd love to hear it