Extra notes about relay state parameter when using idp-first

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@1243 44740490-163a-0410-bde0-09ae8108e29a

docs/simplesamlphp-idp.txt

@@ -767,6 +767,9 @@ Here is an example of such an url:
 
 	https://sp.example.org/simplesaml/saml2/idp/SSOService.php?spentityid=dev.andreas.feide.no
 
+When the IdP-first flow is used an extra parameter is needed in the `saml20-sp-hosted` metadata. This is the `RelayState` parameter that tells the SP which URL to redirect the user to after the user is successfully authenticated. This typically is the frontpage of your application. An example of this can be:
+
+	'RelayState' => '/',
 
 
 B. Writing your own authentication module