Bump to v4.0.0.

internal/baseKeys.js

@@ -0,0 +1,17 @@
+/* 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));
+}
+
+export default baseKeys;