* Add epsilon- and eta-sampling.
Add epsilon- and eta-sampling, following the official code from https://github.com/john-hewitt/truncation-sampling and adapting to be more configurable, as required by Huggingface transformers.
* Add unit tests for epsilon- and eta-sampling.
* Black: fix code formatting.
* Fix docstring spacing.
* Clean up newlines.
* Fix implementation bugs and their associated tests.
* Remove epsilon- and eta-sampling parameters from PretrainedConfig.
* Clarify and clean up the documentation.
* Remove parameters for PretrainedConfig test.
* move generation_*.py src files into generation/*.py
* populate generation.__init__ with lazy loading
* move imports and references from generation.xxx.object to generation.object
