update

node_modules/symbol-observable/es/index.js

@@ -0,0 +1,12 @@
+/* global window */
+import ponyfill from './ponyfill';
+
+var root = this;
+if (typeof global !== 'undefined') {
+	root = global;
+} else if (typeof window !== 'undefined') {
+	root = window;
+}
+
+var result = ponyfill(root);
+export default result;

node_modules/symbol-observable/es/ponyfill.js

@@ -0,0 +1,17 @@
+export default function symbolObservablePonyfill(root) {
+	var result;
+	var Symbol = root.Symbol;
+
+	if (typeof Symbol === 'function') {
+		if (Symbol.observable) {
+			result = Symbol.observable;
+		} else {
+			result = Symbol('observable');
+			Symbol.observable = result;
+		}
+	} else {
+		result = '@@observable';
+	}
+
+	return result;
+};