comment about loading weights in ppo2

baselines/ppo2/ppo2.py

@@ -72,6 +72,7 @@ class Model(object):
             for p, loaded_p in zip(params, loaded_params):
                 restores.append(p.assign(loaded_p))
             sess.run(restores)
+            # If you want to load weights, also save/load observation scaling inside VecNormalize
 
         self.train = train
         self.train_model = train_model