dataset(ncslgr): add initial loading script
Hi @AmitMY, sorry for leaving you hanging for a minute :) 

We've developed a new pipeline for adding datasets with a few extra steps, including adding a dataset card. You can find the full process [here](https://github.com/huggingface/datasets/blob/master/ADD_NEW_DATASET.md)

Would you be up for adding the tags and description in the README.md so we can merge this cool dataset? @lhoestq should be ready for another review :)  Awesome thank you !

It looks like the PR now includes changes from other PR that were previously merged. 
Feel free to create another branch and another PR so that we can have a clean diff.
 Closing for #958 
Its a small dataset, but its heavily annotated
https://www.bu.edu/asllrp/ncslgr.html

![image](https://user-images.githubusercontent.com/5757359/97838609-3c539380-1ce9-11eb-885b-a15d4c91ea49.png)
