v0.31.8

Changes

• release 0.31.8 (#466) @ArneBinder
• make dev dependencies optional (#464) @ArneBinder
• add more auto tests (#457) @ArneBinder

🚀 Features

• add num_val and num_test properties to PieDataModule (#465) @ArneBinder
• add PieDataModule (#463) @ArneBinder

👷 Continuous Integration

• upgrade codecov-action and use CODECOV_TOKEN (#453) @ArneBinder