consider using dask for lazy out-of-core operations on images

[d-v-b]

As a former PIMS user, I found that switching to dask for lazily representing big movies made my life a lot easier. Specifically, functions like this: https://github.com/MouseLand/FaceMap/blob/master/FaceMap/facemap.py#L69 are very concisely represented via operations on dask arrays.

Here's a short example using dask for working with images, and I could give you a short dask demo offline whenever you're free.