Documentation Refresh

Dask has a tremendous amount of well-written documentation, but I am not sure if it is presented effectively (if anyone has any insight on this I'd love to get some data about it). These are some ideas that I am thinking about:

- Fewer pages in the left-nav. I have been seeing other projects make a clearer split between **For Users** and **For Developers/Contributors** I feel like that's a tough split for Dask since there is so much overlap and lots of users end up extending or needing to know about the internals for some other reason. I think that these could be grouped into a page called **Internals** and a lot of the pages that are in **Help and Reference** and **Diagnostics** could be moved into that section.
- Include the new figures from https://github.com/dask/community/issues/135 and make them clickable.
- Use top nav section more effectively. Since that piece is consistent across subprojects, it should consistently point to the most globally useful places.
- Use the right space better. The xarray docs put page level TOC at the right of the page. That feels like a nice improvement to me.
- Make one API Reference rather than separating out Array, Dataframe ... right now there is a lot of duplication between https://docs.dask.org/en/latest/dataframe-api.html#create-dataframes and https://docs.dask.org/en/latest/dataframe-create.html
- Not to pick on dask.dataframe too much, but this TOC is really hard to navigate
 I think it could be improved by removing the section headers from the TOC or somehow moving them up.

I am particularly motivated by the xarray doc refresh. I think their theme looks very nice as well, but I'll save that for another time...

## Current docs
[](https://docs.dask.org/en/latest/)

## Xarray
[](http://xarray.pydata.org/en/stable/)