Add a settings base page in docs

Author: synasius

docs/settings.rst

@@ -0,0 +1,24 @@
+Settings
+========
+
+Our configurations are all namespaced under the `OAUTH2_PROVIDER` settings (yes, like Django REST Framework ;) thanks guys!).
+
+For example:
+
+.. code-block:: python
+
+    OAUTH2_PROVIDER = {
+        'SCOPES': {
+            'read': 'Read scope',
+            'write': 'Write scope',
+        },
+
+        'CLIENT_ID_GENERATOR_CLASS': 'oauth2_provider.generators.ClientIdGenerator',
+
+    }
+
+
+Reference
+=========
+
+TODO: add reference documentation for DOT settings