add more commentary

pypubsub_acl.yaml

@@ -3,12 +3,15 @@
 testuser:
   password: foobar
   acl:
-    # Allow access to events for a private git repository
-    foobar:
+    # Allow sample access to events for a private git repository called privaterepo.git
+    # Topics are AND'ed together and create a common denominator for what the client has access to.
+    # Thus, the below grants access to git/privaterepo.git, but not git/otherrepo.git
+    # You can name/title these segments as you see fit.
+    title_of_my_first_access_segment:
       - git
       - privaterepo.git
     # Allow access to events for dev@example.org mailing list
-    myemails:
+    allow_email_access_for_foobar:
       - email
       - example.org
       - dev