Can't import cc100 dataset
cc100 was added recently, that's why it wasn't available yet.

To load it you can just update `datasets`
```
pip install --upgrade datasets
```

and then you can load `cc100` with

```python
from datasets import load_dataset

lang = "en"
dataset = load_dataset("cc100", lang=lang, split="train")
```
There is some issue to import cc100 dataset.

```
from datasets import load_dataset
dataset = load_dataset("cc100")
```

FileNotFoundError: Couldn't find file at https://raw.githubusercontent.com/huggingface/datasets/1.1.3/datasets/cc100/cc100.py

During handling of the above exception, another exception occurred:

FileNotFoundError                         Traceback (most recent call last)
FileNotFoundError: Couldn't find file at https://s3.amazonaws.com/datasets.huggingface.co/datasets/datasets/cc100/cc100.py

During handling of the above exception, another exception occurred:

FileNotFoundError                         Traceback (most recent call last)
/usr/local/lib/python3.6/dist-packages/datasets/load.py in prepare_module(path, script_version, download_config, download_mode, dataset, force_local_path, **download_kwargs)
    280                 raise FileNotFoundError(
    281                     "Couldn't find file locally at {}, or remotely at {} or {}".format(
--> 282                         combined_path, github_file_path, file_path
    283                     )
    284                 )

FileNotFoundError: Couldn't find file locally at cc100/cc100.py, or remotely at https://raw.githubusercontent.com/huggingface/datasets/1.1.3/datasets/cc100/cc100.py or https://s3.amazonaws.com/datasets.huggingface.co/datasets/datasets/cc100/cc100.py