Introduce Rake and Centroid

Rake is for driving the project's automated tasks and [Centroid](https://github.com/ResourceDataInc/Centroid) helps manage configuration across languages and environments. Rake and Centroid are like teammates that somehow always show up on my team.

This also adds a rake task of `rake ok?` that currently just checks to see the local system has all the necessary environment variables. This could later run tests or whatever is necessary to help with getting a system to the status of OK.