Pie-modules

:rocket: Features

* implement span pair based binary relation classification (task module + model) (91) ArneBinder

* update dependencies (94) ArneBinder

:boom: Breaking Changes

* tokenization saves a mapping from original to new annotations in `added_annotations` (97) ArneBinder

:rocket: Features

* tokenization saves a mapping from original to new annotations in `added_annotations` (97) ArneBinder
* add parameter `return_hidden_states` to `SequenceClassificationModelWithPooler.forward()` (95) ArneBinder

:rotating_light: Testing

* test model parameter values (96) ArneBinder

:rocket: Features

* extend statistics for re_classification_with_indices (92) RainbowRivey

:beetle: Fixes

* fix reverse check for nary relations (90) ArneBinder

:books: Documentation

* list document processing utilities in the README.md (89) ArneBinder

:beetle: Fixes

* fix `RETextClassificationWithIndicesTaskModule` for `NaryRelation` (87) ArneBinder

:rocket: Features

* `NltkSentenceSplitter` returns the result document (85) ArneBinder
* add `NltkSentenceSplitter` (84) ArneBinder

:rocket: Features

* use multi span annotations and documents from PyTorch-IE (82) ArneBinder
* add task lr config for bart_as_pointer_network (81) jk-tripathy