Author vs Contributor Guideline

Need a very clear and concrete way to decide "Author" vs "Contributor".

For now, the FAQ will say:

> 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?