Fsrs

What's Changed
* Remove stratified kfold by L-M-Sherlock in https://github.com/open-spaced-repetition/fsrs-rs/pull/173


**Full Changelog**: https://github.com/open-spaced-repetition/fsrs-rs/compare/v0.6.0...v0.6.1

What's Changed
* Fix/add pub(crate) back by L-M-Sherlock in https://github.com/open-spaced-repetition/fsrs-rs/pull/170
* remove `num_workers` by AlexErrant in https://github.com/open-spaced-repetition/fsrs-rs/pull/171
* Feat/add rules for returning parameters by L-M-Sherlock in https://github.com/open-spaced-repetition/fsrs-rs/pull/172


**Full Changelog**: https://github.com/open-spaced-repetition/fsrs-rs/compare/v0.5.5...v0.6.0

What's Changed
* export simulate & clippy nursery by L-M-Sherlock in https://github.com/open-spaced-repetition/fsrs-rs/pull/169


**Full Changelog**: https://github.com/open-spaced-repetition/fsrs-rs/compare/v0.5.4...v0.5.5

What's Changed
* Speed up optimal_retention() by L-M-Sherlock in https://github.com/open-spaced-repetition/fsrs-rs/pull/168


**Full Changelog**: https://github.com/open-spaced-repetition/fsrs-rs/compare/v0.5.3...v0.5.4

What's Changed
* Minor tweaks to 166 by dae in https://github.com/open-spaced-repetition/fsrs-rs/pull/167


**Full Changelog**: https://github.com/open-spaced-repetition/fsrs-rs/compare/v0.5.2...v0.5.3

What's Changed
* Feat/minimal workload for optimal retention by L-M-Sherlock in https://github.com/open-spaced-repetition/fsrs-rs/pull/165


**Full Changelog**: https://github.com/open-spaced-repetition/fsrs-rs/compare/v0.5.1...v0.5.2