Add okio configuration to okhttp since it depends on it

[ylogx]

[krschultz]

I think we're better off putting a note in the OkHTTP config that you should also include the Okio config.

Unfortunately sometimes I feel like this project has all the pain of maintaining a maven central without any of the tooling. I can see the argument for putting everything that OkHTTP requires in its config, but if we follow that to its conclusion some libraries (e.g. AWS SDK) will end up including practically all the rules in the repo. It's a tough call.