Update the README.

README.md

@@ -17,8 +17,52 @@ add a URL entry for the authentication application:
 ## Settings
 
 There are some additional settings you should add to your Django settings file
-but they're pretty self-explanatory:
+about your OAuth2 client but they're pretty self-explanatory:
 
  * `TEST_OAUTH_CLIENT_ID`: The client ID of your TEST OAuth2 app.
  * `TEST_OAUTH_CLIENT_SECRET`: The client secret of your app.
  * `TEST_OAUTH_CLIENT_CALLBACK`: The _exact_ callback URI of your app.
+
+Some other options are more interesting:
+
+ * `TEST_OAUTH_CREATE_GROUPS`: Create Django groups whenever a user logs into
+   your app.
+ * `TEST_OAUTH_CREATE_CHARACTERS`: Same as above, but creates a Character for
+   each of the alts of the person logging in.
+ * `TEST_OAUTH_REDIRECT`: The URL to which people are redirected after loggin
+   in or out of the app.
+ * `TEST_OAUTH_VERIFIERS`: See below.
+
+### Verifiers
+
+You can use an iterable of `Verifier` objects to confirm that people logging
+into your app conform to some requirement. For example, take the following
+verifier class:
+
+    class GroupMembershipVerifier(Verifier):
+        message = "You are not in the correct groups to log in to this site."
+
+        def valid(self, groups, **kwargs):
+            for g in groups:
+                if g['id'] == self.group:
+                    return True
+
+            return False
+
+You may then use this verifier as follows:
+
+    TEST_OAUTH_VERIFIERS = [
+        verifiers.GroupMembershipVerifier(group=10000)
+    ]
+
+Which will deny any member not in group 10000. A login is denied if any of the
+verifiers return false. So, you may also do something like this:
+
+    TEST_OAUTH_VERIFIERS = [
+        verifiers.GroupMembershipVerifier(group=10000),
+        verifiers.GroupMembershipVerifier(group=1111),
+        verifiers.TESTMembershipVerifier(),
+    ]
+
+You can write your own verifiers as well. Just look at the source code for
+examples.