Update rand requirement from 0.7 to 0.8

[dependabot-preview[bot]]

Updates the requirements on rand to permit the latest version.

Changelog

Sourced from rand's changelog.

[0.8.0] - 2020-12-18

Platform support

• The minimum supported Rust version is now 1.36 (#1011)
• getrandom updated to v0.2 (#1041)
• Remove wasm-bindgen and stdweb feature flags. For details of WASM support, see the getrandom documentation. (#948)
• ReadRng::next_u32 and next_u64 now use little-Endian conversion instead of native-Endian, affecting results on Big-Endian platforms (#1061)
• The nightly feature no longer implies the simd_support feature (#1048)
• Fix simd_support feature to work on current nightlies (#1056)

Rngs

• ThreadRng is no longer Copy to enable safe usage within thread-local destructors (#1035)
• gen_range(a, b) was replaced with gen_range(a..b). gen_range(a..=b) is also supported. Note that a and b can no longer be references or SIMD types. (#744, #1003)
• Replace AsByteSliceMut with Fill and add support for [bool], [char], [f32], [f64] (#940)
• Restrict rand::rngs::adapter to std (#1027; see also #928)
• StdRng: add new std_rng feature flag (enabled by default, but might need to be used if disabling default crate features) (#948)
• StdRng: Switch from ChaCha20 to ChaCha12 for better performance (#1028)
• SmallRng: Replace PCG algorithm with xoshiro{128,256}++ (#1038)

Sequences

• Add IteratorRandom::choose_stable as an alternative to choose which does not depend on size hints (#1057)
• Improve accuracy and performance of IteratorRandom::choose (#1059)
• Implement IntoIterator for IndexVec, replacing the into_iter method (#1007)
• Add value stability tests for seq module (#933)

Misc

• Support PartialEq and Eq for StdRng, SmallRng and StepRng (#979)
• Added a serde1 feature and added Serialize/Deserialize to UniformInt and WeightedIndex (#974)
• Drop some unsafe code (#962, #963, #1011)
• Reduce packaged crate size (#983)
• Migrate to GitHub Actions from Travis+AppVeyor (#1073)

Distributions

• Alphanumeric samples bytes instead of chars (#935)
• Uniform now supports char, enabling rng.gen_range('A'..='Z') (#1068)
• Add UniformSampler::sample_single_inclusive (#1003)

Weighted sampling

• Implement weighted sampling without replacement (#976, #1013)
• rand::distributions::alias_method::WeightedIndex was moved to rand_distr::WeightedAliasIndex. The simpler alternative rand::distribution::WeightedIndex remains. (#945)
• Improve treatment of rounding errors in WeightedIndex::update_weights (#956)
• WeightedIndex: return error on NaN instead of panic (#1005)

Documentation

• Document types supported by random (#994)

Commits

• 98a1aaf Merge pull request #1076 from dhardy/work
• 46082d5 Fix installation of multilib
• d109f18 Update changelog for rand v0.8
• cc93dae Merge pull request #1079 from JJPennington/master
• 9aa8bc1 Modified the StdRng documentation
• 34423a6 Use cp to create redirect
• d4b180d Merge pull request #1078 from rust-random/work2
• 1959b1a Adjust homepage to point at the book
• e9adf45 Switch documentation links to docs.rs
• da3458b Add HTML redirect
• Additional commits viewable in compare view

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