[Feature]Support custom hooks (#305)

* add mytrain.py for test

* test before layers

* test attr in layers

* test classifier

* delete mytrain.py

* register custom_hooks in runner

* set custom_hooks_config to cfg.get(custom_hooks, None)

mmcls/apis/train.py

@@ -127,9 +127,13 @@ def train_model(model,
         optimizer_config = cfg.optimizer_config
 
     # register hooks
-    runner.register_training_hooks(cfg.lr_config, optimizer_config,
-                                   cfg.checkpoint_config, cfg.log_config,
-                                   cfg.get('momentum_config', None))
+    runner.register_training_hooks(
+        cfg.lr_config,
+        optimizer_config,
+        cfg.checkpoint_config,
+        cfg.log_config,
+        cfg.get('momentum_config', None),
+        custom_hooks_config=cfg.get('custom_hooks', None))
     if distributed:
         runner.register_hook(DistSamplerSeedHook())