Addition of Nl2Bash Dataset
Hello, thanks. I had a talk with the dataset authors, found out that the data now is obsolete and they'll get a stable version soon. So temporality closing the PR.
 Although I have a question, What should _id_ be in the return statement? Should that be something like a start index (or) the type of split will do? Thanks.  @reshinthadithyan we should hold off on this for a couple of weeks till NeurIPS concludes. The [NLC2CMD](http://nlc2cmd.us-east.mybluemix.net/) data will be out then; which includes a cleaner version of this NL2Bash data. The older data is sort of obsolete now.  Ah nvm you already commented 😆 
## Overview
The NL2Bash data contains over 10,000 instances of linux shell commands and their corresponding natural language descriptions provided by experts, from the Tellina system. The dataset features 100+ commonly used shell utilities.
## Footnotes
The following dataset marks the first ML on source code related Dataset in datasets module. It'll be really useful as a lot of the research direction involves Transformer Based Model.
Thanks.
### Reference Links

> Paper Link = https://arxiv.org/pdf/1802.08979.pdf 
> Github Link = https://github.com/TellinaTool/nl2bash





