Update README about keystone usage

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

README.md

@@ -13,6 +13,8 @@ Install
 
 2) Alter your proxy-server.conf pipeline to have swift3:
 
+If you use tempauth:
+
     Was::
 
         [pipeline:main]
@@ -23,8 +25,27 @@ Install
         [pipeline:main]
         pipeline = catch_errors cache swift3 tempauth proxy-server
 
+If you use keystone:
+
+    Was::
+
+        [pipeline:main]
+        pipeline = catch_errors cache authtoken keystone proxy-server
+
+    Change To::
+
+        [pipeline:main]
+        pipeline = catch_errors cache swift3 s3token authtoken keystone proxy-server
+
 3) Add to your proxy-server.conf the section for the Swift3 WSGI filter::
 
     [filter:swift3]
     use = egg:swift3#swift3
 
+You also need to add the following if you use keystone (adjust port, host, protocol configurations for your environment):
+
+    [filter:s3token]
+    paste.filter_factory = keystone.middleware.s3_token:filter_factory
+    auth_port = 35357
+    auth_host = 127.0.0.1
+    auth_protocol = http