Add kaldi version numbers to version.json and /__version__ endpoint

[pdehaan]

Currently, the https://speaktome.stage.mozaws.net/__version__ endpoint gives me the following:

{
  commit: "e872e3a69dbac583a1fcc41d12c9bc1ba711705a",
  version: "v1.0.2",
  source: "https://github.com/mozilla/speech-proxy",
  build: "https://circleci.com/gh/mozilla/speech-proxy/69"
}

It'd be nice if we could get some information about the commit SHA for the kaldi servers as well or something. Currently it is very difficult/impossible to tell when a new version of the kaldi servers have been deployed.

[ghost]

this is a good idea