Updated docs with expire.

Author: Simon Prickett

README.md

@@ -119,6 +119,9 @@ print(andrew.pk)
 # We can save the model to Redis by calling `save()`:
 andrew.save()
 
+# Expire the model after 2 mins (120 seconds)
+andrew.expire(120)
+
 # To retrieve this customer with its primary key, we use `Customer.get()`:
 assert Customer.get(andrew.pk) == andrew
 ```

docs/getting_started.md

@@ -553,6 +553,15 @@ andrew = Customer(
 andrew.save()
 ```
 
+## Expiring Models
+
+We can expire an instance of a model using `expire`, and passing it the number of seconds after which we want the instance to expire in Redis:
+
+```python
+# Expire Andrew in 2 minutes (120 seconds)
+andrew.expire(120)
+```
+
 ## Examining Your Data In Redis
 
 You can view the data stored in Redis for any Redis OM model.