[BUG] Added xarray to dependecies

[s-weigand]

The notebook 07.01-ipyleaflet.ipynb uses xarray, which isn't part of the dependencies and thus Advanced example 1: Velocity can't be executed on binder.

IMHO adding netcdf4 to the normal dependencies and making the download code for the wind-global.nc dataset a code cell instead of an instruction in a markdown cell would be an improvement.

[mwcraig]

Thanks, @s-weigand. Any chance you could also make the change you mentioned to the notebook? I think the reason we had it that way was, in part, that the hotel WiFi at SciPy, while good, crumbled under too much simultaneous load.

Not an issue when the conference is distributed!

Other tutorial folks, if this looks good to you too please go ahead and merge.

[s-weigand]

Yeah WiFi at conferences ... 😆
And sure I can make the changes.
The only question would be if you would prefer the download code or just add the file and reference it, the source repo is under MIT license.

[mwcraig]

Let's go with the download code; some day we'll be able to be in person again and we don't want the repo to get too big.

[s-weigand]

I made the velocity map the last statement of the input cell, so it is shown in the output cell as well as in the Sidecar.
IMHO this is more consistent with the other examples, than just showing it in the Sidecar.

[s-weigand]

Btw. I use Review Notebook App in projects where people collaborate on notebooks. This makes it easier for maintainers to spot differences in notebooks, since the can look at a rendered diff, instead of the json blob.