Add a badge to this repo using shields.io that says Deprecated

Add this text as a h2 somewhere near the top of readme

## Deprecated

This repository contains code/an approach that has been deprecated.

See: X for an updated repo.

///

"X" is a placeholder for an updated repo and can be a Shields.io badge. Ask the user if there is an updated repo and to provide the URL. Replace X with this repo if one exists. If not, don't add that line.