GitLab

- support mbart-en-ro weights
- add MBartTokenizer

* add t5 docs basis

* improve docs

* add t5 docs

* improve t5 docstring

* add t5 tokenizer docstring

* finish docstring

* make style

* add pretrained models

* correct typo

* make examples work

* finalize docs

`generate` code that produces 99% identical summarizations to fairseq on CNN test data, with caching.

* Results same as fairseq
* Wrote a ton of tests
* Struggled with api signatures
* added some docs

cc @lysandrejik

converted from https://github.com/openai/gpt-2-output-dataset/tree/master/detector

Co-Authored-By: Lysandre Debut <lysandre.debut@reseau.eseo.fr>
Co-Authored-By: Jong Wook Kim <jongwook@nyu.edu>
Co-Authored-By: Jeff Wu <wuthefwasthat@gmail.com>