Beta 0.2.8 (many improvements)

• Robustify automatic batch_size and epochs selection
• Robustify automatic learning_rate selection based on lr-range-test
• Improve train optimizer and scheduler
• soft-start regularization in last third of training
• Improve reqularization function for all components
• allow custom optimizer and loss_func
• support python 3.6.9 for colab
• Crossvalidation utility
• Chinese documentation
• support callable loss
• Robustify changepoints data format
• require log_level in logger util
• Rename tqdm, remove overbleed option
• Reg schedule: increasing regularization in last third of training
• bug fix in plot country holidays
• Add Energy datasets and example notebook
• disable log file by default
• add double crossvalidation
• improve tests
• Buxfixes