Bump to v4.0.0.

internal/getSymbols.js

@@ -0,0 +1,15 @@
+/** Built-in value references. */
+var getOwnPropertySymbols = Object.getOwnPropertySymbols;
+
+/**
+ * Creates an array of the own symbol properties of `object`.
+ *
+ * @private
+ * @param {Object} object The object to query.
+ * @returns {Array} Returns the array of symbols.
+ */
+var getSymbols = getOwnPropertySymbols || function() {
+  return [];
+};
+
+export default getSymbols;