Merge amethyst#142

142: Update hashbrown requirement from 0.3.0 to 0.4.0 r=torkleyy a=dependabot-preview[bot]

Updates the requirements on [hashbrown](https://github.com/rust-lang/hashbrown) to permit the latest version.
<details>
<summary>Changelog</summary>

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

> ## [v0.4.0] - 2019-05-30
> 
> ### Fixed
> - Fixed `Send` trait bounds on `IterMut` not matching the libstd one. ([amethyst#82](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/82))
> 
> ## [v0.3.1] - 2019-05-30
> 
> ### Fixed
> - Fixed incorrect use of slice in unsafe code. ([amethyst#80](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/80))
> 
> ## [v0.3.0] - 2019-04-23
> 
> ### Changed
> - Changed shrink_to to not panic if min_capacity < capacity. ([amethyst#67](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/67))
> 
> ### Fixed
> - Worked around emscripten bug emscripten-core/emscripten-fastcomp#258. ([amethyst#66](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/66))
> 
> ## [v0.2.2] - 2019-04-16
> 
> ### Fixed
> - Inlined non-nightly lowest_set_bit_nonzero. ([amethyst#64](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/64))
> - Fixed build on latest nightly. ([amethyst#65](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/65))
> 
> ## [v0.2.1] - 2019-04-14
> 
> ### Changed
> - Use for_each in map Extend and FromIterator. ([amethyst#58](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/58))
> - Improved worst-case performance of HashSet.is_subset. ([amethyst#61](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/61))
> 
> ### Fixed
> - Removed incorrect debug_assert. ([amethyst#60](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/60))
> 
> ## [v0.2.0] - 2019-03-31
> 
> ### Changed
> - The code has been updated to Rust 2018 edition. This means that the minimum
>   Rust version has been bumped to 1.31 (2018 edition).
> 
> ### Added
> - Added `insert_with_hasher` to the raw_entry API to allow `K: !(Hash + Eq)`. ([amethyst#54](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/54))
> - Added support for using hashbrown as the hash table implementation in libstd. ([amethyst#46](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/46))
> 
> ### Fixed
> - Fixed cargo build with minimal-versions. ([amethyst#45](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/45))
> - Fixed `#[may_dangle]` attributes to match the libstd `HashMap`. ([amethyst#46](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/46))
> - ZST keys and values are now handled properly. ([amethyst#46](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/46))
> 
> ## [v0.1.8] - 2019-01-14
> 
></tr></table> ... (truncated)
</details>
<details>
<summary>Commits</summary>

- [`987b962`](rust-lang/hashbrown@987b962) Version 0.4.0
- [`a9ddbcf`](rust-lang/hashbrown@a9ddbcf) Auto merge of [amethyst#82](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/82) - Amanieu:itermut_send, r=Amanieu
- [`a4eba4f`](rust-lang/hashbrown@a4eba4f) Fix the bounds on K for the Send impl of IterMut
- [`1889600`](rust-lang/hashbrown@1889600) Version 0.3.1
- [`c765ea0`](rust-lang/hashbrown@c765ea0) Auto merge of [amethyst#80](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/80) - RalfJung:raw, r=Amanieu
- [`2693d12`](rust-lang/hashbrown@2693d12) cast the entire slice to a raw pointer, not just the first element
- [`4368aa4`](rust-lang/hashbrown@4368aa4) Auto merge of [amethyst#78](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/78) - RalfJung:miri, r=Amanieu
- [`419f2ac`](rust-lang/hashbrown@419f2ac) skip Miri tests if the setup fails
- [`538d149`](rust-lang/hashbrown@538d149) Merge pull request [amethyst#77](https://github-redirect.dependabot.com/rust-lang/hashbrown/issues/77) from lzutao/refresh-doc
- [`70afa1b`](rust-lang/hashbrown@70afa1b) Use docs.rs badge
- Additional commits viewable in [compare view](rust-lang/hashbrown@v0.3.0...v0.4.0)
</details>
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Cargo.toml

@@ -20,7 +20,7 @@ travis-ci = { repository = "torkleyy/shred" }
 
 [dependencies]
 arrayvec = "0.4"
-hashbrown = "0.3.0"
+hashbrown = "0.4.0"
 mopa = "0.2"
 rayon = { version = "1.0", optional = true }
 smallvec = "0.6"