I removed some lint configuration in the process:
* `#[allow(clippy::suspicious_else_formatting)]` because nothing is
currently triggering it.
* `#[warn(clippy::future_not_send)]` because some stuff under
`src/lib.rs` is. And also like, auto-trait leakage generally means
this isn't a problem, and if things really need to be `Send`, then
you'll probably know to mark it manually.
* `#[warn(rust_2018_idioms)]` and replaced it with
`explicit-outlives-requirements = "warn"` which is the most useful
lint in that group that isn't enabled by default.
3e389256f5