Bump to v4.0.0.

internal/baseKeys.js

@@ -0,0 +1,20 @@
+define([], function() {
+
+  /* Built-in method references for those with the same name as other `lodash` methods. */
+  var nativeKeys = Object.keys;
+
+  /**
+   * The base implementation of `_.keys` which doesn't skip the constructor
+   * property of prototypes or treat sparse arrays as dense.
+   *
+   * @private
+   * @type Function
+   * @param {Object} object The object to query.
+   * @returns {Array} Returns the array of property names.
+   */
+  function baseKeys(object) {
+    return nativeKeys(Object(object));
+  }
+
+  return baseKeys;
+});