[add] doc to use list of wsse

Author: diegoug

docs/wsse.rst

@@ -37,3 +37,19 @@ Example usage::
 
 .. _xmlsec: https://pypi.python.org/pypi/xmlsec
 .. _README: https://github.com/mehcode/python-xmlsec
+
+
+UsernameToken and Signature together
+------------------------------------
+
+To use UsernameToken and Signature together, then you can pass both together
+to the client in a list
+
+    >>> from zeep import Client
+    >>> from zeep.wsse.username import UsernameToken
+    >>> user_name_token = UsernameToken('username', 'password'))
+    >>> signature = Signature(private_key_filename, public_key_filename,
+    ...     optional_password))
+    >>> client = Client(
+    ...     'http://www.webservicex.net/ConvertSpeed.asmx?WSDL',
+    ...     wsse=[user_name_token, signature])