Bump to v4.0.0.

internal/copySymbols.js

@@ -0,0 +1,16 @@
+define(['./copyObject', './getSymbols'], function(copyObject, getSymbols) {
+
+  /**
+   * Copies own symbol properties of `source` to `object`.
+   *
+   * @private
+   * @param {Object} source The object to copy symbols from.
+   * @param {Object} [object={}] The object to copy symbols to.
+   * @returns {Object} Returns `object`.
+   */
+  function copySymbols(source, object) {
+    return copyObject(source, getSymbols(source), object);
+  }
+
+  return copySymbols;
+});