The `atty` crate seems unmaintained. There's
https://rustsec.org/advisories/RUSTSEC-2021-0145 filed against it,
which `cargo-deny` complains about. A fix for that has been open for
well over a year without being fixed
(https://github.com/softprops/atty/pull/51). It turns out the
functionality is also available via the `crossterm` crate (thanks,
@yuja), which we already depend on.
Since we also depend on `atty` via `clap`, I also added an exception
to the `cargo-deny` config.
Our current version of `cpufeatures` was yanked so we needed to
upgrade at least that. Note that I had to add "UNICODE-DFS-2016" as an
allowed license for `cargo-deny`. I also had to upgrade `chrono` from
0.4.20 to 0.4.22 in the `Cargo.toml` files to prevent `cargo update`
from *downgrading* it in the lock file.
