Resolve deprecation warning by updating react-modal

Warning: ModalPortal: React.createClass is deprecated and will be removed in version 16. Use plain JavaScript classes instead. If you're not yet ready to migrate, create-react-class is available on npm as a drop-in replacement.

index.html

@@ -22,7 +22,7 @@
 	<script src="https://unpkg.com/react@15/dist/react.js"></script>
 	<script src="https://unpkg.com/react-dom@15/dist/react-dom.js"></script>
 	<script src="https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.18.1/babel.min.js"></script>
-	<script src="https://cdnjs.cloudflare.com/ajax/libs/react-modal/1.6.5/react-modal.js"></script>
+	<script src="https://cdnjs.cloudflare.com/ajax/libs/react-modal/1.7.7/react-modal.js" integrity="sha256-wQ9go2p9/RzvdqC0RzS2djz4aujaK10VA5UnV9A5eXI=" crossorigin="anonymous"></script>
 	<script src="bower_components/d3/d3.min.js"></script>
 	<script src="bower_components/lodash/lodash.js"></script>
 	<script src="bower_components/graphlib/dist/graphlib.core.js"></script>