function fetch(hash){
  return $.ajax({
    method: "GET",
    url: baseURL + "/gists/" + hash
  }).then(function(response) {
    try {
      return JSON.parse(response.files['schema.json'].content);
    } catch (e) {
      return $.Deferred().reject(e);
    }
  });
}
Accepts gist hash (ID of the gist) and return a promise that resolves to gist `schema.json` file content.
@see https://developer.github.com/v3/gists/#get-a-single-gist