Add hotpot QA
Awesome :) 

Don't pay attention to the RemoteDatasetTest error, I'm fixing it right now You can rebase from master to fix the CI test :) If we're lucky we can even include this dataset in today's release Just thinking since `type` can only be `comparison` or `bridge` and `level` can only be `easy`, `medium`, `hard` should they be `ClassLabel`? > Just thinking since `type` can only be `comparison` or `bridge` and `level` can only be `easy`, `medium`, `hard` should they be `ClassLabel`?

I think it's more a tag than a label. I guess a string is fine

Added the [HotpotQA](https://github.com/hotpotqa/hotpot) multi-hop question answering dataset.

