Add server_info documentation.

Author: Rémy HUBSCHER

README.rst

@@ -82,6 +82,20 @@ at creation time, so that this value will be used by default.
     client = Client(bucket="payments", collection="receipts", auth=auth)
 
 
+Getting server information
+--------------------------
+
+You can use the ``server_info`` methods to get the server information::
+
+.. code-block:: python
+
+    from kinto_client import Client
+
+    client = Client(server_url='http://localhost:8888/v1')
+    infos = client.server_info()
+    assert 'schema' in infos['capabilities'], "Server doesn't supports schema validation."
+
+
 Handling buckets
 ----------------