Update README with new profile functionality

Author: jamesls

README.rst

@@ -95,6 +95,33 @@ you can try::
     TABLENAMES     Second
     TABLENAMES     Third
 
+Profiles
+--------
+
+The aws-shell supports AWS CLI profiles.  You have two options to use
+profiles.  First, you can provide a profile when you start the aws-shell::
+
+    $ aws-shell --profile prod
+    aws>
+
+When you do this all the server side completion as well as CLI commands
+you run will automatically use the ``prod`` profile.
+
+You can also change the current profile while you're in the aws-shell::
+
+    $ aws-shell
+    aws> .profile demo
+    Current shell profile changed to: demo
+
+You can also check what profile you've configured in the aws-shell using::
+
+    aws> .profile
+    Current shell profile: demo
+
+After changing your profile using the ``.profile`` dot command, all
+server side completion as well as CLI commands will automatically use
+the new profile you've configured.
+
 
 Features
 ========