changelog and docco for secure topics

CHANGELOG.md

@@ -1,5 +1,6 @@
 # 0.7.2
 - Addessed an issue with SQS not updating in real-time, only when backlog is requested.
+- Added secure topics feature for locking publishing of certain pubsub topics to the ACL. 
 
 # 0.7.1
 - Use asyncio queues for modifying the list of events pending publishing to avoid potential race conditions.

README.md

@@ -19,6 +19,7 @@
   * [Pushing a private event](#pushing-a-private-event)
   * [Retrieving private events](#retrieving-private-events)
   * [LDAP-based ACL](#ldap-based-acl)
+  * [Securing certain topics](#securing-certain-topics)
 - [Working with Amazon SQS](#working-with-amazon-sqs)
 - [Persistent backlogs](#persistent-backlogs)
 - [License](#license)
@@ -263,6 +264,21 @@ PyPubSub supports ACL via asynchronous LDAP, either through group memberships or
 
 See `pypubsub.yaml` for an LDAP example.
 
+### Securing certain topics
+You can secure topics, meaning only authenticated users with special credentials may post using 
+those topics. To do so, you will need to edit the `secure_topics`  list in the `clients` section of 
+your configuration file, for instance:
+
+~~~yaml
+clients:
+  secure_topics:
+    - bread
+    - syrup
+~~~
+The above would lock publishing the topics `bread` and `syrup` for anyoen not specifically allowed
+ to use those topics in their ACL segment. Users or LDAP groups can be allowed topics via the 
+`topics` directive in their ACL segment. See the `pypubsub_acl.yaml` file for an example.
+
 ## Working with Amazon SQS
 PyPubSub supports AWS SQS for weaving in payloads from their server-less Simple Queue Services.
 Multiple queues can be supported and items pushed to SQS will seamlessly appear in the