Worked example is confusing if worked at standalone without instructor input

[qiUip]

There are multiple things in the worked example which might be hard for someone following alone outside the workshop setting to understand within some more explanation. While we can provide that in the workshop, it might be useful to include this directly in the notebook?

In particular:

1. The use of Unitful - Perhaps we could add some text explaining what it does?
2. Some additional information about Optim could be provided in the notebook to explain (a) the existence of the dropdown; (b) the syntax going into the optimize function.

Do we care about this? If so I'll be happy to add a few lines into the notebook to address the above, but if we only really intend for this notebook to live within the setting of a taught workshop we can leave it as is.

[giordano]

Thanks for the suggestions! I pushed some changes in 982d1f1 which I hope address the main concerns.