Update vulnerable dependencies

This brings the number of vulnerable dependencies down from 8 to 1.
The remaining vulnerability can't be easily fixed:

```
> cargo tree -i generic-array:0.12.3
generic-array v0.12.3
├── block-buffer v0.7.3
│   └── sha-1 v0.8.2
│       [build-dependencies]
│       └── pest_meta v2.1.3
│           └── pest_generator v2.1.3
│               └── pest_derive v2.1.0 (proc-macro)
│                   ├── comrak v0.9.1
│                   │   └── docs-rs v0.6.0 (/home/joshua/src/rust/docs.rs)
│                   └── tera v1.5.0
│                       └── docs-rs v0.6.0 (/home/joshua/src/rust/docs.rs)
└── digest v0.8.1
    └── sha-1 v0.8.2 (*)
```

`pest` or `sha-1` will need to release a new version that depends on a
fixed version of generic-array.

Here's a list of all changes:

```
$ cat updates.txt
comrak
futures-core
futures-util
generic-array:0.12.3
generic-array:0.14.3
hyper:0.10.16
hyper:0.13.6
pest_derive
pest_generator
pest_meta
sha-1
smallvec:0.6.13
smallvec:1.4.0
time:0.2.16
$ xargs -n1 cargo update -p < updates.txt
    Updating arc-swap v0.4.6 -> v0.4.8
    Updating futures-core v0.3.5 -> v0.3.13
    Updating futures-channel v0.3.5 -> v0.3.13
    Updating futures-io v0.3.5 -> v0.3.13
    Updating futures-macro v0.3.5 -> v0.3.13
    Updating futures-sink v0.3.5 -> v0.3.13
    Updating futures-task v0.3.5 -> v0.3.13
    Updating futures-util v0.3.5 -> v0.3.13
      Adding pin-project-lite v0.2.4
    Updating proc-macro-hack v0.5.15 -> v0.5.19
    Updating generic-array v0.14.3 -> v0.14.4
      Adding cfg-if v1.0.0
      Adding httpdate v0.3.2
    Updating hyper v0.13.6 -> v0.13.10
      Adding pin-project v1.0.5
      Adding pin-project-internal v1.0.5
    Updating proc-macro2 v1.0.13 -> v1.0.24
    Updating syn v1.0.22 -> v1.0.60
      Adding tracing v0.1.25
      Adding tracing-core v0.1.17
    Updating smallvec v0.6.13 -> v0.6.14
    Updating smallvec v1.4.0 -> v1.6.1
      Adding const_fn v0.4.5
    Updating time v0.2.16 -> v0.2.25
```

Here are the previous warnings:

```
> cargo audit
    Fetching advisory database from `https://github.com/RustSec/advisory-db.git`
      Loaded 249 security advisories (from /home/joshua/.local/lib/cargo/advisory-db)
    Updating crates.io index
    Scanning Cargo.lock for vulnerabilities (417 crate dependencies)
error: Vulnerable crates found!

ID:       RUSTSEC-2020-0091
Crate:    arc-swap
Version:  0.4.6
Date:     2020-12-10
URL:      https://rustsec.org/advisories/RUSTSEC-2020-0091
Title:    Dangling reference in `access::Map` with Constant
Solution:  upgrade to >= 1.1.0 OR >= 0.4.8
Dependency tree:
arc-swap 0.4.6
├── signal-hook-registry 1.2.0
│   └── tokio 0.2.22
│       ├── tokio-util 0.3.1
│       │   ├── tokio-postgres 0.5.5
│       │   │   └── postgres 0.17.5
│       │   │       ├── schemamama_postgres 0.3.0
│       │   │       │   └── docs-rs 0.6.0
│       │   │       ├── r2d2_postgres 0.16.0
│       │   │       │   └── docs-rs 0.6.0
│       │   │       └── docs-rs 0.6.0
│       │   └── h2 0.2.5
│       │       └── hyper 0.13.6
│       ├── tokio-tls 0.3.1
│       │   ├── reqwest 0.10.6
│       │   │   ├── rustwide 0.11.0
│       │   │   │   └── docs-rs 0.6.0
│       │   │   └── docs-rs 0.6.0
│       │   └── hyper-tls 0.4.1
│       │       ├── rusoto_core 0.45.0
│       │       │   ├── rusoto_s3 0.45.0
│       │       │   │   └── docs-rs 0.6.0
│       │       │   └── docs-rs 0.6.0
│       │       └── reqwest 0.10.6
│       ├── tokio-postgres 0.5.5
│       ├── rustwide 0.11.0
│       ├── rusoto_signature 0.45.0
│       │   └── rusoto_core 0.45.0
│       ├── rusoto_credential 0.45.0
│       │   ├── rusoto_signature 0.45.0
│       │   ├── rusoto_core 0.45.0
│       │   └── docs-rs 0.6.0
│       ├── rusoto_core 0.45.0
│       ├── reqwest 0.10.6
│       ├── postgres 0.17.5
│       ├── hyper-tls 0.4.1
│       ├── hyper 0.13.6
│       ├── h2 0.2.5
│       └── docs-rs 0.6.0
└── docs-rs 0.6.0

ID:       RUSTSEC-2020-0060
Crate:    futures-task
Version:  0.3.5
Date:     2020-09-04
URL:      https://rustsec.org/advisories/RUSTSEC-2020-0060
Title:    futures_task::waker may cause a use-after-free if used on a type that isn't 'static
Solution:  upgrade to >= 0.3.6
Dependency tree:
futures-task 0.3.5
├── futures-util 0.3.5
│   ├── rustwide 0.11.0
│   │   └── docs-rs 0.6.0
│   ├── reqwest 0.10.6
│   │   ├── rustwide 0.11.0
│   │   └── docs-rs 0.6.0
│   ├── hyper 0.13.6
│   ├── h2 0.2.5
│   │   └── hyper 0.13.6
│   ├── futures-executor 0.3.5
│   │   └── futures 0.3.5
│   │       ├── tokio-postgres 0.5.5
│   │       │   └── postgres 0.17.5
│   │       │       ├── schemamama_postgres 0.3.0
│   │       │       │   └── docs-rs 0.6.0
│   │       │       ├── r2d2_postgres 0.16.0
│   │       │       │   └── docs-rs 0.6.0
│   │       │       └── docs-rs 0.6.0
│   │       ├── rusoto_signature 0.45.0
│   │       │   └── rusoto_core 0.45.0
│   │       │       ├── rusoto_s3 0.45.0
│   │       │       │   └── docs-rs 0.6.0
│   │       │       └── docs-rs 0.6.0
│   │       ├── rusoto_s3 0.45.0
│   │       ├── rusoto_credential 0.45.0
│   │       │   ├── rusoto_signature 0.45.0
│   │       │   ├── rusoto_core 0.45.0
│   │       │   └── docs-rs 0.6.0
│   │       ├── rusoto_core 0.45.0
│   │       └── postgres 0.17.5
│   ├── futures 0.3.5
│   └── docs-rs 0.6.0
├── futures-executor 0.3.5
└── futures 0.3.5

ID:       RUSTSEC-2020-0059
Crate:    futures-util
Version:  0.3.5
Date:     2020-10-22
URL:      https://rustsec.org/advisories/RUSTSEC-2020-0059
Title:    MutexGuard::map can cause a data race in safe code
Solution:  upgrade to >= 0.3.7
Dependency tree:
futures-util 0.3.5
├── rustwide 0.11.0
│   └── docs-rs 0.6.0
├── reqwest 0.10.6
│   ├── rustwide 0.11.0
│   └── docs-rs 0.6.0
├── hyper 0.13.6
├── h2 0.2.5
│   └── hyper 0.13.6
├── futures-executor 0.3.5
│   └── futures 0.3.5
│       ├── tokio-postgres 0.5.5
│       │   └── postgres 0.17.5
│       │       ├── schemamama_postgres 0.3.0
│       │       │   └── docs-rs 0.6.0
│       │       ├── r2d2_postgres 0.16.0
│       │       │   └── docs-rs 0.6.0
│       │       └── docs-rs 0.6.0
│       ├── rusoto_signature 0.45.0
│       │   └── rusoto_core 0.45.0
│       │       ├── rusoto_s3 0.45.0
│       │       │   └── docs-rs 0.6.0
│       │       └── docs-rs 0.6.0
│       ├── rusoto_s3 0.45.0
│       ├── rusoto_credential 0.45.0
│       │   ├── rusoto_signature 0.45.0
│       │   ├── rusoto_core 0.45.0
│       │   └── docs-rs 0.6.0
│       ├── rusoto_core 0.45.0
│       └── postgres 0.17.5
├── futures 0.3.5
└── docs-rs 0.6.0

ID:       RUSTSEC-2020-0146
Crate:    generic-array
Version:  0.12.3
Date:     2020-04-09
URL:      https://rustsec.org/advisories/RUSTSEC-2020-0146
Title:    arr! macro erases lifetimes
Solution:  upgrade to >= 0.14.0
Dependency tree:
generic-array 0.12.3

ID:       RUSTSEC-2021-0020
Crate:    hyper
Version:  0.13.6
Date:     2021-02-05
URL:      https://rustsec.org/advisories/RUSTSEC-2021-0020
Title:    Multiple Transfer-Encoding headers misinterprets request payload
Solution:  upgrade to >= 0.14.3 OR ^0.13.10
Dependency tree:
hyper 0.13.6

ID:       RUSTSEC-2021-0003
Crate:    smallvec
Version:  0.6.13
Date:     2021-01-08
URL:      https://rustsec.org/advisories/RUSTSEC-2021-0003
Title:    Buffer overflow in SmallVec::insert_many
Solution:  upgrade to >= 0.6.14, < 1.0.0 OR >= 1.6.1
Dependency tree:
smallvec 0.6.13

ID:       RUSTSEC-2021-0003
Crate:    smallvec
Version:  1.4.0
Date:     2021-01-08
URL:      https://rustsec.org/advisories/RUSTSEC-2021-0003
Title:    Buffer overflow in SmallVec::insert_many
Solution:  upgrade to >= 0.6.14, < 1.0.0 OR >= 1.6.1
Dependency tree:
smallvec 1.4.0

ID:       RUSTSEC-2020-0071
Crate:    time
Version:  0.2.16
Date:     2020-11-18
URL:      https://rustsec.org/advisories/RUSTSEC-2020-0071
Title:    Potential segfault in the time crate
Solution:  upgrade to >= 0.2.23
Dependency tree:
time 0.2.16
```

Author: jyn514