Explain the language modelling format in RoBERTa pretraining readme
Explain the language modelling format in RoBERTa pretraining readme

Summary: Pull Request resolved: https://github.com/pytorch/fairseq/pull/1174

Differential Revision: D17627767

Pulled By: myleott

fbshipit-source-id: 7b5f77146b8776a5967699e430136039c066c851

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq