Bump to v4.0.0.

internal/createSet.js

@@ -0,0 +1,15 @@
+import Set from './Set';
+import noop from '../noop';
+
+/**
+ * Creates a set of `values`.
+ *
+ * @private
+ * @param {Array} values The values to add to the set.
+ * @returns {Object} Returns the new set.
+ */
+var createSet = !(Set && new Set([1, 2]).size === 2) ? noop : function(values) {
+  return new Set(values);
+};
+
+export default createSet;