Lazy Slicing

[willow-ahrens]

It would be great to have support for lazy windowing operations. in particular, we could push the windows earlier into the computation to avoid redundant work.

[ingridtomovski]

To implement lazy windowing you could make a function that creates a window from a given dataset and window size and a function that processes a window. By calling these two functions you won't have to create and process all windows at one time, but only when needed.