Initial review

The most recent commit message is so accurate.

We wound up shying away from this pattern in sync, and instead just have some lightweight tweens that write logging and metrics as json data to stdout.  It simplifies the config and the ops stack, while providing a bit of robustness by using the filesystem to decouple us from heka.  Worth a conversation with Katie and whd, but if they're happy with what we have in sync then I'd recommend a similar approach here to simplify things.

(Totally open to arguments against that approach though, we could easily be doing it wrong in sync!)

Whatever we end up with, I'd like to see it in `mozsvc` rather than in project-specific repos, so that we can get it right once and re-use it everywhere.