roly: moving window median

[Keith Goodman]

A few us started a new project to study the performance of various
moving window median algorithms and implementations. We'll be using
the bottleneck list to discuss the project.

I think of the project as a temporary one. Once we have the results,
anyone is free (BSD) to implement the results. I plan to do so in
bottleneck.

Please join us! The repo: https://github.com/kwgoodman/roly