code: function start(callback) {
      var dbDeferred = Q.defer();
      config = defaultConfig;
  
      if (typeof gmeConfig.rest.components[CONFIG_ID] === 'object' &&
          gmeConfig.rest.components[CONFIG_ID].options) {
  
          config = gmeConfig.rest.components[CONFIG_ID].options;
      }
  
      mongodb.MongoClient.connect(config.mongo.uri, config.mongo.options, function (err, db) {
          if (err) {
              dbDeferred.reject(err);
          } else {
              dbConn = db;
              dbDeferred.resolve();
          }
      });
  
      return dbDeferred.promise.nodeify(callback);
  }
docs: Called before the server starts listening.
  @param {function} callback