Kurobako

What's Changed
* Fix Study._log_completed_trial call by c-bata in https://github.com/optuna/kurobako-py/pull/18
* Fix bugs in kurobako/solver/optuna.py by contramundum53 in https://github.com/optuna/kurobako-py/pull/19


**Full Changelog**: https://github.com/optuna/kurobako-py/compare/0.2.0...0.2.1

What's Changed
* Use optuna.Study.ask/tell instead of BaseStorage.set_trial_values etc. by contramundum53 in https://github.com/optuna/kurobako-py/pull/16
* Remove unused file `optuna_multi_objective.py` by sile in https://github.com/optuna/kurobako-py/pull/17

New Contributors
* contramundum53 made their first contribution in https://github.com/optuna/kurobako-py/pull/16

**Full Changelog**: https://github.com/optuna/kurobako-py/compare/0.1.12...0.2.0