Add EarlyStop documentation (#245)

* Update Training Loop.md

* Update index.md

* Update README.md

* Update Training Loop.md

* Update Training Loop.md

docs/Trainer/Training Loop.md

@@ -19,6 +19,24 @@ It can be useful to force training for a minimum number of epochs or limit to a
 trainer = Trainer(min_nb_epochs=1, max_nb_epochs=1000)
 ```
 
+---
+#### Early stopping
+To enable ealry-stopping, define the callback and give it to the trainer.
+``` {.python}
+from pytorch_lightning.callbacks import EarlyStopping
+
+# DEFAULTS
+early_stop_callback = EarlyStopping(
+    monitor='val_loss',
+    min_delta=0.00,
+    patience=0,
+    verbose=False,
+    mode='auto'
+)
+
+trainer = Trainer(early_stop_callback=early_stop_callback)
+```
+
 ---
 #### Force disable early stop 
 Use this to turn off early stopping and run training to the [max_epoch](#force-training-for-min-or-max-epochs)