WIP - Recommended Pairings

I'm going to start work on a system to generated 'recommended' matches. My goal is to consider the following:
* Recommended matches should be with players that you play less frequently
* Recommended matches should be with players that have similar ratings with you

For now, I'm just going to return JSON to the browser. After this works, we can worry how this gets called, and how players are informed.

Please give feedback. Since I'm just getting started things are most flexible right now.