Format files using rustfmt

[Rolv-Apneseth]

Split from #16

I guess I'll do these sequentially? They'll all be conflicting otherwise. If you don't want this format one let me know and I'll move on to the clippy warnings.

[fenhl]

I'm going to need some time to review this. My first impression is that a lot of the changes are making things harder to read, for example the inconsistency introduced in the asserts, and the extra braces around match arm bodies. I'll have to do some research on why rustfmt does these things.

[Rolv-Apneseth]

Sure thing, take your time. Maybe for more consistent asserts I could increase the line length to something that keeps them all on one line. Personally I think the changes make it more readable but of course that's just personal preference and this is not my project so I have no issue skipping this formatting step.