update readme to reflect our inability to produce encrypted assertions

re #179

README.md

@@ -142,7 +142,7 @@ The SAML standard is huge and complex with many dark corners and strange, unused
 
 This package supports the **Web SSO** profile. Message flows from the service provider to the IDP are supported using the **HTTP Redirect** binding and the **HTTP POST** binding. Message flows from the IDP to the service provider are supported via the **HTTP POST** binding.
 
-The package supports signed and encrypted SAML assertions. It does not support signed or encrypted requests.
+The package can produce signed SAML assertions, and can validate both signed and encrypted SAML assertions. It does not support signed or encrypted requests.
 
 ## RelayState