Created dataset card snli.md
First draft of a dataset card using the SNLI corpus as an example.

This is mostly based on the [Google Doc draft](https://docs.google.com/document/d/1dKPGP-dA2W0QoTRGfqQ5eBp0CeSsTy7g2yM8RseHtos/edit), but I added a few sections and moved some things around. 

- I moved **Who Was Involved** to follow **Language**, both because I thought the authors should be presented more towards the front and because I think it makes sense to present the speakers close to the language so it doesn't have to be repeated.

- I created a section I called **Data Characteristics** by pulling some things out of the other sections. I was thinking that this would be more about the language use in context of the specific task construction. That name isn't very descriptive though and could probably be improved.
-- Domain and language type out of **Language**. I particularly wanted to keep the Language section as simple and as abstracted from the task as possible.
-- 'How was the data collected' out of **Who Was Involved** 
-- Normalization out of **Features/Dataset Structure** 
-- I also added an annotation process section.

- I kept the **Features** section mostly the same as the Google Doc, but I renamed it **Dataset Structure** to more clearly separate it from the language use, and added some links to the documentation pages. 

- I also kept **Tasks Supported**,  **Known Limitations**, and **Licensing Information** mostly the same. Looking at it again though, maybe **Tasks Supported** should come before **Data Characteristics**?

The trickiest part about writing a dataset card for the SNLI corpus specifically is that it's built on datasets which are themselves built on datasets so I had to dig in a lot of places to find information. I think this will be easier with other datasets and once there is more uptake of dataset cards so they can just link to each other. (Maybe that needs to be an added section?)

I also made an effort not to repeat information across the sections or to refer to a previous section if the information was relevant in a later one. Is there too much repetition still?