Cargo.toml: Update rand and rand_core to 0.8 and 0.6

[mxinden]

See rand changelog and rand_core changelog.

Thanks for maintaining snow!

[mcginty]

Thanks!

[mxinden]

Thanks @mcginty for merging this pull request, updating all remaining outdated dependencies and cutting a release.

As far as I can tell v0.7.3 includes breaking changes and should thus not have been a patch release, but a minor release (v0.8.0). More specifically this crate exposes parts of rand on its public API. rand introduced breaking changes between v0.7 and v0.8 and thus snow introduces breaking changes between v0.7.2 and v0.7.3. The v0.7.3 snow release thus breaks any builds directly depending on both snow and rand, e.g. the rust-libp2p project.

@mcginty could you yank v0.7.3 and instead release the same source code as v0.8.0?

[mcginty]

@mxinden oh wow, yep. Yanked. I'll hold these changes until v0.8.0 along with these last few open PRs.

Sorry if that caused any annoyances in your project.

[mxinden]

Yanked

Thank you for the swift resolution.

I'll hold these changes until v0.8.0 along with these last few open PRs.

Sounds good to me.