Merge wasmerio#808

808: Bump rand from 0.7.0 to 0.7.2 r=MarkMcCaskey a=dependabot-preview[bot]

Bumps [rand](https://github.com/rust-random/rand) from 0.7.0 to 0.7.2.
<details>
<summary>Changelog</summary>

*Sourced from [rand's changelog](https://github.com/rust-random/rand/blob/master/CHANGELOG.md).*

> ## [0.7.2] - 2019-09-16
> ### Fixes
> - Fix dependency on `rand_core` 0.5.1 ([wasmerio#890](https://github-redirect.dependabot.com/rust-random/rand/issues/890))
> 
> ### Additions
> - Unit tests for value stability of distributions added ([wasmerio#888](https://github-redirect.dependabot.com/rust-random/rand/issues/888))
> 
> ## [0.7.1] - 2019-09-13
> ### Fixes
> - Fix `no_std` behaviour, appropriately enable c2-chacha's `std` feature ([wasmerio#844](https://github-redirect.dependabot.com/rust-random/rand/issues/844))
> - `alloc` feature in `no_std` is available since Rust 1.36 ([wasmerio#856](https://github-redirect.dependabot.com/rust-random/rand/issues/856))
> - Fix or squelch issues from Clippy lints ([wasmerio#840](https://github-redirect.dependabot.com/rust-random/rand/issues/840))
> 
> ### Additions
> - Add a `no_std` target to CI to continously evaluate `no_std` status ([wasmerio#844](https://github-redirect.dependabot.com/rust-random/rand/issues/844))
> - `WeightedIndex`: allow adjusting a sub-set of weights ([wasmerio#866](https://github-redirect.dependabot.com/rust-random/rand/issues/866))
</details>
<details>
<summary>Commits</summary>

- [`249ebfc`](rust-random/rand@249ebfc) Merge pull request [wasmerio#888](https://github-redirect.dependabot.com/rust-random/rand/issues/888) from dhardy/master
- [`5ac4cbd`](rust-random/rand@5ac4cbd) Prepare rand 0.7.2
- [`f39915a`](rust-random/rand@f39915a) rand_distr: work around tan func issue
- [`802ba8f`](rust-random/rand@802ba8f) rand_distr: add missing value_stability tests
- [`a43d7f1`](rust-random/rand@a43d7f1) Fix tests
- [`2ef2e66`](rust-random/rand@2ef2e66) Add value_stability tests for uniform
- [`096a5dd`](rust-random/rand@096a5dd) UniformSampler: add doc on usage of sample_single
- [`f78781a`](rust-random/rand@f78781a) Uniform: replace inner field with struct tuple
- [`856fdfb`](rust-random/rand@856fdfb) Distribution: add doc of portability
- [`72af6f8`](rust-random/rand@72af6f8) Add value_stability tests for bernoulli, int, float and other distrs
- Additional commits viewable in [compare view](rust-random/rand@0.7.0...0.7.2)
</details>
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