Licensing Guidelines

Need a document describing how to license datasets and covering various licensing questions.

For now, FAQ will say:

> ### I downloaded and edited a dataset. How do I give the original author credit? Am I now the "author"?
>
> You're not the new author. Authorship constitutes the main creators of a dataset. Add yourself to the "contributors" list. You will also be the "maintainer" of datasets published under your account. We know it is a bit unclear what makes up an "Author" vs a "Contributor", but we're hoping to define a good guideline for this ([see the conversation here](https://github.com/jbenet/datadex/issue/29)). Perhaps ask the original authors what they think?
> ### How do I know what license my dataset has?
>
> If you're creating a dataset from scratch, you can pick whatever you want (see below).
>
> If you're modifying another dataset, we recommend keeping the same license. Please make sure modification and re-publishing is allowed by the original license. This is usually the case, but someone may publish datasets with non-permissive licenses that shouldn't be violated.
>
> It's best to check. Consider:
> - asking the original author
> - asking [our mailing list](https://groups.google.com/forum/#!forum/data-discuss)
> - asking [on github](https://github.com/jbenet/datadex/issues/new)
> ### I'm publishing a Dataset. What license should I pick?
>
> We recommend using one of the popular open-source licenses. These websites can help you find out more and pick the right license for you:
> - http://creativecommons.org/choose/
> - http://choosealicense.com/
> - http://opendatacommons.org/
> - http://www.dcc.ac.uk/sites/default/files/documents/how-to-license-data.pdf
> ### I made a subset of a dataset. Can I publish that and who is the author?
>
> It depends on the original dataset's license. Some licenses are very permissive. Some are not. If you're not sure, we recommend
> - asking the original author
> - asking [our mailing list](https://groups.google.com/forum/#!forum/data-discuss)
>
> We hope to iron out the licensing concerns with a straight-foward guide. [See the conversation here](https://github.com/jbenet/datadex/issues/30).