externalLoader = function (type, location, options, cb) {
        return _.isString(location) ? util.fetchJson(type, location, options, function (err, data) {
            if (err) {
                return cb(err);
            }

            return cb(null, extractModel(data, type));
        }) : cb(null, extractModel(location, type));
    }
Loads the given data of type from a specified external location

@param {String} type - The type of data to load.
@param {String} location - The location to load from (file path or URL).
@param {Object} options - The set of wrapped options.
@param {function} cb - The callback function whose invocation marks the end of the external load routine.
@returns {*}