Issue: winogrande cannot be dowloaded 

Hi,
I am getting this error when trying to run the codes on the cloud.  Thank you for any suggestion and help on this @lhoestq 

```
 File "./finetune_trainer.py", line 318, in <module>
    main()
  File "./finetune_trainer.py", line 148, in main
    for task in data_args.tasks]
  File "./finetune_trainer.py", line 148, in <listcomp>
    for task in data_args.tasks]
  File "/workdir/seq2seq/data/tasks.py", line 65, in get_dataset
    dataset = self.load_dataset(split=split)
  File "/workdir/seq2seq/data/tasks.py", line 466, in load_dataset
    return datasets.load_dataset('winogrande', 'winogrande_l', split=split)
  File "/usr/local/lib/python3.6/dist-packages/datasets/load.py", line 589, in load_dataset
    path, script_version=script_version, download_config=download_config, download_mode=download_mode, dataset=True
  File "/usr/local/lib/python3.6/dist-packages/datasets/load.py", line 267, in prepare_module
    local_path = cached_path(file_path, download_config=download_config)
  File "/usr/local/lib/python3.6/dist-packages/datasets/utils/file_utils.py", line 308, in cached_path
    use_etag=download_config.use_etag,
  File "/usr/local/lib/python3.6/dist-packages/datasets/utils/file_utils.py", line 487, in get_from_cache
    raise ConnectionError("Couldn't reach {}".format(url))
ConnectionError: Couldn't reach https://raw.githubusercontent.com/huggingface/datasets/1.1.3/datasets/winogrande/winogrande.py
yo/0 I1224 14:17:46.419031 31226 main shadow.py:122 > Traceback (most recent call last):
  File "/usr/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/usr/local/lib/python3.6/dist-packages/torch/distributed/launch.py", line 260, in <module>
    main()
  File "/usr/local/lib/python3.6/dist-packages/torch/distributed/launch.py", line 256, in main
    cmd=cmd)
```

Comments:
I have same issue for other datasets (`myanmar_news` in my case).

A version of `datasets` runs correctly on my local machine (**without GPU**) which looking for the dataset at 
```
https://raw.githubusercontent.com/huggingface/datasets/master/datasets/myanmar_news/myanmar_news.py
```

Meanwhile, other version runs on Colab (**with GPU**) failed to download the dataset. It try to find the dataset at `1.1.3` instead of `master` . If I disable GPU on my Colab, the code can load the dataset without any problem.

Maybe there is some version missmatch with the GPU and CPU version of code for these datasets?

It looks like they're two different issues

----------

First for `myanmar_news`: 

It must come from the way you installed `datasets`.
If you install `datasets` from source, then the `myanmar_news` script will be loaded from `master`.
However if you install from `pip` it will get it using the version of the lib (here `1.1.3`) and `myanmar_news` is not available in `1.1.3`.

The difference between your GPU and CPU executions must be the environment, one seems to have installed `datasets` from source and not the other.

----------

Then for `winogrande`:

The errors says that the url https://raw.githubusercontent.com/huggingface/datasets/1.1.3/datasets/winogrande/winogrande.py is not reachable.
However it works fine on my side.

Does your machine have an internet connection ? Are connections to github blocked by some sort of proxy ?
Can you also try again in case github had issues when you tried the first time ?