initial commit for MultiReQA 
Added MultiReQA, which is a dataset containing the sentence boundary annotation from eight publicly available QA datasets including SearchQA, TriviaQA, HotpotQA, NaturalQuestions, SQuAD, BioASQ, RelationExtraction, and TextbookQA. 
looks like this dataset includes changes about many other files than the ones for multi_re_qa

Can you create another branch and another PR please ? > looks like this dataset includes changes about many other files than the ones for multi_re_qa
> 
> Can you create another branch and another PR please ?

Sure I will do that. Thank you.