Update rand requirement from 0.7 to 0.8

[dependabot]

Updates the requirements on rand to permit the latest version.

Changelog

Sourced from rand's changelog.

[0.7.3] - 2020-01-10

Fixes

• The Bernoulli distribution constructors now reports an error on NaN and on denominator == 0. (#925)
• Use std::sync::Once to register fork handler, avoiding possible atomicity violation (#928)
• Fix documentation on the precision of generated floating-point values

Changes

• Unix: make libc dependency optional; only use fork protection with std feature (#928)

Additions

• Implement std::error::Error for BernoulliError (#919)

[0.7.2] - 2019-09-16

Fixes

• Fix dependency on rand_core 0.5.1 (#890)

Additions

• Unit tests for value stability of distributions added (#888)

[0.7.1] - 2019-09-13

Yanked

This release was yanked since it depends on rand_core::OsRng added in 0.5.1 but specifies a dependency on version 0.5.0 (#890), causing a broken builds when updating from rand 0.7.0 without also updating rand_core.

Fixes

• Fix no_std behaviour, appropriately enable c2-chacha's std feature (#844)
• alloc feature in no_std is available since Rust 1.36 (#856)
• Fix or squelch issues from Clippy lints (#840)

Additions

• Add a no_std target to CI to continuously evaluate no_std status (#844)
• WeightedIndex: allow adjusting a sub-set of weights (#866)

[0.7.0] - 2019-06-28

Fixes

• Fix incorrect pointer usages revealed by Miri testing (#780, #781)
• Fix (tiny!) bias in Uniform for 8- and 16-bit ints (#809)

Crate

• Bumped MSRV (min supported Rust version) to 1.32.0
• Updated to Rust Edition 2018 (#823, #824)
• Removed dependence on rand_xorshift, rand_isaac, rand_jitter crates (#759, #765)
• Remove dependency on winapi (#724)
• Removed all build.rs files (#824)
• Removed code already deprecated in version 0.6 (#757)
• Removed the serde1 feature (It's still available for backwards compatibility, but it does not do anything. #830)
• Many documentation changes

... (truncated)

Commits

• 074cb6a Merge pull request #929 from dhardy/master
• 0f4e152 Prepare rand 0.7.3 release
• 5b0d874 Merge pull request #928 from dhardy/libc
• ae4683c Remove use of deprecated ATOMIC_USIZE_INIT
• ae3a416 Fix #911: use Once instead of AtomicBool
• a67173e make libc dependency optional (fork protection requires std)
• e2dc2c3 Merge pull request #926 from dhardy/fmt
• fab964d Manual function specification reformatting
• 3a5d5a8 Use rustfmt::skip for some cases
• 3a51c3e Manual array reformatting
• Additional commits viewable in compare view

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