Code style

[kpp]

Use common style, probably add rustfmt hook to CI to check the style.

[fare]

https://github.com/rust-lang-nursery/fmt-rfcs/blob/master/guide/guide.md

[fare]

I propose we adopt the above style guide (first Google result for "rust style guide").

We should indeed probably add rustfmt to a pre-commit hook and/or part of the default build & test commands.