Merge pull request #505 from marcvanzee/pipy

Update CHANGELOG: Add new header for v0.2.2

CHANGELOG.md

@@ -1,6 +1,21 @@
 Changelog
 ----------
 
+vNext
+----
+ (Please add entries here with your changes for the next version)
+ - ...
+
+v0.2.2
+----
+ - Added Reinforcement Learning example (examples/ppo).
+ - Fix Adafactor bug that prevented factorization.
+ - Fix scan broadcast issue in functional core.
+ - Fix initialization RNGs to work with omnistaging for jitted inits.
+ - Replaces usage of 'param' kind to 'params' collection.
+ - Fix LARS optimizer for zero param initialization.
+ - Added various examples in Linen API. See [README.md](https://github.com/google/flax/blob/master/flax/linen/README.md) for more information.
+ - Full JAX omnistaging compatibility.
 
 v0.2
 ----
@@ -9,7 +24,6 @@ v0.2
  - Optimizers broken out into separate directory with base class and implementations.
  - traverse_util added flatten_dict and unflatten_dict utility methods for nested dicts.
 
-
 v0.1
 ----