Thanks for several comments pointing out the unclearness of what's being "more modern". I've updated the README to be: "The advantage of Mark over S-expression

Thanks for several comments pointing out the unclearness of what's being "more modern". I've updated the README to be: "The advantage of Mark over S-expressions is that it takes a more modern, JS-first approach in its design, and can be more conveniently used in web and node.js environments." Hope it's clearer now.