I came across https://github.com/NixOS/hydra/issues/751 and realized
that hydra-notify is responsible for creating the additional jobsets in
a declarative file. My declarative testing works in dev now.
runHyda automatically starts hydra and postgres:
```
$ nix-shell -A runHydra
```
The shell receives hydra from the working copy as buildInput.
Running hydra, queue-runner, evaluator and postgres is managed
by foreman (https://github.com/ddollar/foreman) and configured
in `Procfile`.
