Fix clippy warnings + uprade some audited deps

[fenollp]

Note: some audited deps are not simple to upgrade (and weren't). This needs further work:

λ cargo audit
    Fetching advisory database from `https://github.com/RustSec/advisory-db.git`
      Loaded 561 security advisories (from /home/pete/.cargo/advisory-db)
    Updating crates.io index
    Scanning Cargo.lock for vulnerabilities (134 crate dependencies)
Crate:     rustc-serialize
Version:   0.3.24
Title:     Stack overflow in rustc_serialize when parsing deeply nested JSON
Date:      2022-01-01
ID:        RUSTSEC-2022-0004
URL:       https://rustsec.org/advisories/RUSTSEC-2022-0004
Solution:  No fixed upgrade is available!
Dependency tree:
rustc-serialize 0.3.24
├── num-rational 0.1.42
│   └── num 0.1.42
│       └── stopwatch 0.0.7
│           └── libremarkable 0.6.0
├── num-complex 0.1.43
│   └── num 0.1.42
└── num-bigint 0.1.44
    ├── num-rational 0.1.42
    └── num 0.1.42

Crate:     time
Version:   0.1.45
Title:     Potential segfault in the time crate
Date:      2020-11-18
ID:        RUSTSEC-2020-0071
URL:       https://rustsec.org/advisories/RUSTSEC-2020-0071
Severity:  6.2 (medium)
Solution:  Upgrade to >=0.2.23
Dependency tree:
time 0.1.45
└── chrono 0.4.26
    └── libremarkable 0.6.0

Crate:     rusttype
Version:   0.9.3
Warning:   unmaintained
Title:     rusttype is Unmaintained
Date:      2021-04-01
ID:        RUSTSEC-2021-0140
URL:       https://rustsec.org/advisories/RUSTSEC-2021-0140
Dependency tree:
rusttype 0.9.3
└── libremarkable 0.6.0

error: 2 vulnerabilities found!
warning: 1 allowed warning found

Also: shouldn't we be setting dependency versions with broader constraints than an exact version number? e.g: "1.0" or "1"? Lib consumers then should be able to upgrade their own deps before eventually making PRs against this repo

[LinusCDE]

Thanks for making and mentioning it. Should have been merged a while ago ig. Just checked that current rust was still happy and fixed the new clippy lint error.

Lgtm!

[LinusCDE]

If no issues are raised in the next few days, lets just merge this ig.

[bkirwi]

These are great!

(I should have more time to stay on top of changes like these soon, but also don't feel the need to block on me for them!)