Note preload_metadata removal

CHANGELOG.md

@@ -6,4 +6,11 @@ jwalk now runs the majority of `walkdir`s tests.
 Second major change is the walk can now be parameterized with a client state
 type. This state can be manipulated from the `process_read_dir` callback and
 then is passed down when reading descendens with the `process_read_dir`
-callback.
+callback.
+
+Part of this second change is that `preload_metadata` option is removed. That
+means `DirEntry.metadata()` is never a cached value. Instead you want to read
+metadata you should do it in the `process_entries` callback and store whatever
+values you need as `client_state`. See this [benchmark] as an example.
+
+[benchmark]: https://github.com/jessegrosjean/jwalk/blob/master/benches/walk_benchmark.rs#L45