Example: Scikit-image and trackpy (bubble tracking in foams)

[Emmanuelle Gouillart]

> Do we want to create a new page on the website with collections of nice iPython notebooks?

The problem would be to maintain this notebooks. I would rather advocate
to cut the tutorials into shorter examples for the gallery (that can also
be downloaded as notebooks), and to integrate the "best" notebooks into
the user guide, to be sure that the code is maintained. 

But we could also have a list of links of nice notebooks hosted elsewhere.

Just my 2 cents,
Emma