Return metadata with JSON response

[mre]

Currently we return the raw data when the analytics endpoint is called. It would be helpful for troubleshooting to also include a metadata section.

Example:

{
  "meta": {
    // arbitrary metadata fields, e.g. date, state (success, error),...
  },
  "result": {
    // previous response goes here
  }
}

[mre]

Done in #66.