Start community-provided dataset docs
can you also reference the `--organization` flag like in https://github.com/huggingface/transformers/blob/master/docs/source/model_sharing.rst#upload-your-model-with-the-cli ? done! Not sure if the changes in `datasets/wmt_t2t/wmt_utils.py` are intentional.
If you want to add more configs to wmt, could you do it in a serapate PR ? I don't think I changed wmt_utils (I think github is wrong or my setup is poorly configured).

Locally git diff master --name-only says one file. Master is up to date.
Tried to make a new PR #755 and the same thing happened. Trying new fork.
This is one I did to get the pseudo-labels updated. Not sure if it generalizes, but I figured I would write it down. It was pretty easy because all I had to do was make properly formatted directories and change URLs.

+ In slack @thomwolf  called it a `user-namespace` dataset, but the docs call it `community dataset`.
I think the first naming is clearer, but I didn't address that here.


+ I didn't add metadata, will try that.