Updated Client compatibility list (markdown)

Client-compatibility-list.md

@@ -44,6 +44,20 @@ boto.connect_s3(aws_access_key_id = 'identity',
     host = '127.0.0.1', port = 8080, is_secure = False,
     calling_format = boto.s3.connection.OrdinaryCallingFormat())
 ```
+
+### [boto3](https://github.com/boto/boto3)
+
+```python
+session = boto3.session.Session(aws_access_key_id='identity',
+                                aws_secret_access_key='credential')
+# low level S3 client
+client = session.client('s3', endpoint_url='http://localhost:8080',
+                        config=boto3.session.Config(s3={'addressing_style': 'path'}))
+# S3 resource object
+resource = session.resource('s3', endpoint_url='http://localhost:8080',
+                            config=boto3.session.Config(s3={'addressing_style': 'path'}))
+```
+
 ### [fog](https://github.com/fog/fog)
 
 ```ruby