Move to using black as the formatter

[lossyrob]

In #309 I've added type annotations everywhere, which end up with some pretty lengthy lines in things like method signatures. I don't think yapf, the current formatter, is handling these situations well

I've been using black in other projects with similar annotations with a lot of success. I'd like to move to it as the formatter for the project.

I'd prefer to do this as a last change in #309. This will cause the diff to be extensive, but as of right now with all the type annotation additions most of the code has changed anyway.

Let me know if there's any objections on this issue, otherwise I'll proceed with that plan and close out this issue with #309.