function notImplemented(method) {
    if (!method.throws) {
        return function returns() {
            return method.returns;
        };
    } else {
        return function throws() {
            throw new Error('Method ' + method.name + ' is not implemented!');
        };
    }
}
A function generator for all programatically attaching methods on to
the ServerUpgradeResponse class.

@private
@function notImplemented
@param    {Object}   method - an object containing configuration
@returns  {Function} function