Adjustable Jupyter example

[manthey]

Demonstrate adjusting an algorithm with a widget (like a slider for a float parameter) in a Jupyter notebook. Postitive pixel count is a good example to start with.

This involves figuring out how to expose a slider widget that will rerun a process on change (and be debounced appropriately).

Eventually, it would be also show hooking this through to running the algorithm via Girder.