blake2 v0.11.0 release tracking issue

[tarcieri]

This tracks the next stable release of the blake2 crate.

[tarcieri]

I would like to propose releasing blake2 as-is. There are a few open PRs (e.g. #906) which could potentially be considered. That said, it's a blocker for the next argon2 release which I get frequently asked about.

I would really like to refactor blake2 as well (see #228 which I'm unlikely to pursue in its current form at this point as it's quite stale) but I think it would be better to release a version that's compatible with digest v0.11 and then follow up with a blake2 v0.12.0 which still uses digest v0.11 but includes the desired refactoring (e.g. new SIMD backends).