Save / Load Hyperparameters with checkpoint (#415)

* Save and load hparams from checkpoints

* Update docs

* Add warning when not saving hparams

* Missing import

* Update .run_local_tests.sh

* Update lm_test_module_mixins.py

* Update lightning_module_template.py

pl_examples/basic_examples/lightning_module_template.py

@@ -158,7 +158,7 @@ class LightningTemplateModel(LightningModule):
             val_loss = output['val_loss']
 
             # reduce manually when using dp
-            if self.trainer.use_dp:
+            if self.trainer.use_dp or self.trainer.use_ddp2:
                 val_loss = torch.mean(val_loss)
             val_loss_mean += val_loss