Adding NewsQA dataset

Since the dataset has legal restrictions to circulate the original data. It has to be manually downloaded by the user and loaded to the library. 

Comments:
Generate the dummy dataset then regenerate the dataset_info.json file, 

> Generate the dummy dataset then regenerate the dataset_info.json file,

The pytest scripts do not accept manual directory inputs for the data provided manually. This is why the tests fail. 

don't use the --auto-generate argument and you will get a brief instructions on how to create dummy data for your dataset,
also you dont have to run the pytest for main dataset if your data is needed to be downloaded manually, just run the pytest for dummy dataset, and when you will create the json you need to provide the main data directory path by using this argument --data_dir

Thanks for your help, @tanmoyio 
I tried with and without --auto_generate flag. 
Here are the issues. 

**With --auto_generate**
`python datasets-cli dummy_data datasets/newsqa/ --auto_generate `
`Traceback (most recent call last):
  File "datasets-cli", line 36, in <module>
    service.run()
  File "/Users/sanjaykamath/Python_Projects/HuggingFace/datasets/src/datasets/commands/dummy_data.py", line 321, in run
    keep_uncompressed=self._keep_uncompressed,
  File "/Users/sanjaykamath/Python_Projects/HuggingFace/datasets/src/datasets/commands/dummy_data.py", line 340, in _autogenerate_dummy_data
    dataset_builder._split_generators(dl_manager)
  File "/Users/sanjaykamath/.cache/huggingface/modules/datasets_modules/datasets/newsqa/7a565b204506c1fd91047290073be54d3ae05fa2b0ab17ae0bc6f709350fcbca/newsqa.py", line 180, in _split_generators
    path_to_manual_folder = os.path.abspath(os.path.expanduser(dl_manager.manual_dir))
  File "/Users/sanjaykamath/anaconda3/envs/huggingface/lib/python3.7/posixpath.py", line 235, in expanduser
    path = os.fspath(path)
TypeError: expected str, bytes or os.PathLike object, not NoneType
`


**Without --auto_generate**
`python datasets-cli dummy_data datasets/newsqa/`
`Dataset  with config BuilderConfig(name='combined-csv', version=1.0.0, data_dir=None, data_files=None, description='This part of the dataset covers the whole dataset in the combined format of CSV as mentioned here: https://github.com/Maluuba/newsqa#csv') seems to already open files in the method `_split_generators(...)`. You might consider to instead only open files in the method `_generate_examples(...)` instead. If this is not possible the dummy data has to be created with less guidance. Make sure you create the file None.
Traceback (most recent call last):
  File "datasets-cli", line 36, in <module>
    service.run()
  File "/Users/sanjaykamath/Python_Projects/HuggingFace/datasets/src/datasets/commands/dummy_data.py", line 326, in run
    dataset_builder=dataset_builder, mock_dl_manager=mock_dl_manager
  File "/Users/sanjaykamath/Python_Projects/HuggingFace/datasets/src/datasets/commands/dummy_data.py", line 406, in _print_dummy_data_instructions
    for split in generator_splits:
UnboundLocalError: local variable 'generator_splits' referenced before assignment
`


Excellent comments. Thanks @lhoestq for your valuable comments. 
I've changed everything you had mentioned and the tests pass now. 
Let me know if something still needs to be changed. 

Thank you very much @lhoestq @tanmoyio @yjernite @thomwolf for all your support :)