Added conv ai 2 (Again)
Looking perfect to me, need to rerun the tests
 Thanks, @tanmoyio. 
How do I rerun the tests? Should I change something or push a new commit? @rkc007 you don't need to rerun it, @lhoestq @yjernite will rerun it, as there are huge number of PRs in the queue it might take lil bit of time.  ive just re-run the tests Thank you @abhishekkrthakur. Can you please rerun it again? It seems something was broken in CI during the previous test. @lhoestq Sorry for the mess. I don't know why this keeps on happening. I tried step by step process of updating the PR but seems something is wrong. This happened for 2nd time with the same PR. Apologies for that. 

New PR -> https://github.com/huggingface/datasets/pull/1527
Also, I fixed everything in the new PR.
The original PR -> https://github.com/huggingface/datasets/pull/1383

Reason for creating again - 

The reason I had to create the PR again was due to the master rebasing issue. After rebasing the changes, all the previous commits got added to the branch. 