[Dataset requests] New datasets for Text Classification

We are missing a few datasets for Text Classification which is an important field.

Namely, it would be really nice to add:
- [x] TREC-6 dataset (see here for instance: https://pytorchnlp.readthedocs.io/en/latest/source/torchnlp.datasets.html#torchnlp.datasets.trec_dataset)  **[done]**
  - #386
- [x] Yelp-5
  - #1315
- [x] Movie review (Movie Review (MR) dataset [156]) **[done (same as rotten_tomatoes)]**
- [x] SST (Stanford Sentiment Treebank) **[include in glue]**
  - #1934
- [ ] Multi-Perspective Question Answering (MPQA) dataset **[require authentication (indeed manual download)]**
- [x] Amazon. This is a popular corpus of product reviews collected from the Amazon website [159]. It contains labels for both binary classification and multi-class (5-class) classification
  - #791
  - #1389
- [x] 20 Newsgroups. The 20 Newsgroups dataset  **[done]**
  - #410 
- [x] Sogou News dataset **[done]**
  - #450
- [x] Reuters news. The Reuters-21578 dataset [165] **[done]**
  - #471 
- [x] DBpedia. The DBpedia dataset [170]
  - #1116
- [ ] Ohsumed. The Ohsumed collection [171] is a subset of the MEDLINE database
- [ ] EUR-Lex. The EUR-Lex dataset
- [x] WOS. The Web Of Science (WOS) dataset **[done]**
  - #424
- [ ] PubMed. PubMed [173]
- [x] TREC-QA: TREC-6 + TREC-50
  - See above: TREC-6 dataset
- [x] Quora. The Quora dataset [180]
  - #366

All these datasets are cited in https://arxiv.org/abs/2004.03705

Pinging @mariamabarham as well

- `nlp` has MR! It's called `rotten_tomatoes`
- SST is part of GLUE, or is that just SST-2?
- `nlp` also has `ag_news`, a popular news classification dataset

I'd also like to see:
- the Yahoo Answers topic classification dataset
- the Kaggle Fake News classification dataset

Thanks @jxmorris12 for pointing this out. 

In glue we only have SST-2 maybe we can add separately SST-1.


This is the homepage for the Amazon dataset: https://www.kaggle.com/datafiniti/consumer-reviews-of-amazon-products

Is there an easy way to download kaggle datasets programmatically? If so, I can add this one!

Hi @jxmorris12 for now I think our `dl_manager` does not download from Kaggle.
@thomwolf , @lhoestq

Pretty sure the quora dataset is the same one I implemented here: https://github.com/huggingface/nlp/pull/366

Great list. Any idea if Amazon Reviews has been added?

- ~40 GB of text (sadly no emoji)
- popular MLM pre-training dataset before bigger datasets like WebText https://arxiv.org/abs/1808.01371
- turns out that binarizing the 1-5 star rating leads to great Pos/Neg/Neutral dataset, T5 paper claims to get very high accuracy (98%!) on this with small amount of finetuning https://arxiv.org/abs/2004.14546

Apologies if it's been included (great to see where) and if not, it's one of the better medium/large NLP dataset for semi-supervised learning, albeit a bit out of date. 

Thanks!! 

cc @sshleifer 

On the Amazon Reviews dataset, the original UCSD website has noted these are now updated to include product reviews through 2018 -- actually quite recent compared to many other datasets. Almost certainly the largest NLP dataset out there with labels!
https://jmcauley.ucsd.edu/data/amazon/ 

Any chance someone has time to onboard this dataset in a HF way?

cc @sshleifer 

@albertvillanova How up to date is this issue? I see that some of these datasets are now on huggingface but have not been checked off the list