Issue: Dataset "dane" missing

the `dane` dataset appear to be missing in the latest version (1.1.3).

```python
>>> import datasets
>>> datasets.__version__
'1.1.3'
>>> "dane" in datasets.list_datasets()
True
```

As we can see it should be present, but doesn't seem to be findable when using `load_dataset`.

```python
>>> datasets.load_dataset("dane")
Traceback (most recent call last):
  File "/home/kenneth/.Envs/EDP/lib/python3.8/site-packages/datasets/load.py", line 267, in prepare_module
    local_path = cached_path(file_path, download_config=download_config)
  File "/home/kenneth/.Envs/EDP/lib/python3.8/site-packages/datasets/utils/file_utils.py", line 300, in cached_path
    output_path = get_from_cache(
  File "/home/kenneth/.Envs/EDP/lib/python3.8/site-packages/datasets/utils/file_utils.py", line 486, in get_from_cache
    raise FileNotFoundError("Couldn't find file at {}".format(url))
FileNotFoundError: Couldn't find file at https://raw.githubusercontent.com/huggingface/datasets/1.1.3/datasets/dane/dane.py

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/kenneth/.Envs/EDP/lib/python3.8/site-packages/datasets/load.py", line 278, in prepare_module
    local_path = cached_path(file_path, download_config=download_config)
  File "/home/kenneth/.Envs/EDP/lib/python3.8/site-packages/datasets/utils/file_utils.py", line 300, in cached_path
    output_path = get_from_cache(
  File "/home/kenneth/.Envs/EDP/lib/python3.8/site-packages/datasets/utils/file_utils.py", line 486, in get_from_cache
    raise FileNotFoundError("Couldn't find file at {}".format(url))
FileNotFoundError: Couldn't find file at https://s3.amazonaws.com/datasets.huggingface.co/datasets/datasets/dane/dane.py

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/kenneth/.Envs/EDP/lib/python3.8/site-packages/datasets/load.py", line 588, in load_dataset
    module_path, hash = prepare_module(
  File "/home/kenneth/.Envs/EDP/lib/python3.8/site-packages/datasets/load.py", line 280, in prepare_module
    raise FileNotFoundError(
FileNotFoundError: Couldn't find file locally at dane/dane.py, or remotely at https://raw.githubusercontent.com/huggingface/datasets/1.1.3/datasets/dane/dane.py or https://s3.amazonaws.com/datasets.huggingface.co/datasets/datasets/dane/dane.py
```

This issue might be relevant to @ophelielacroix from the Alexandra Institut whom created the data.

Comments:
Hi @KennethEnevoldsen ,
I think the issue might be that this dataset was added during the community sprint and has not been released yet. It will be available with the v2 of datasets.
For now, you should be able to load the datasets after installing the latest (master) version of datasets using pip:
pip install git+https://github.com/huggingface/datasets.git@master

The `dane` dataset was added recently, that's why it wasn't available yet. We did an intermediate release today just before the v2.0.

To load it you can just update `datasets`
```
pip install --upgrade datasets
```

and then you can load `dane` with

```python
from datasets import load_dataset

dataset = load_dataset("dane")
```

Thanks. Solved the problem.