be consistent with strftime time formatting

Author: harrisony

lib/onelogin/ruby-saml/logoutrequest.rb

@@ -35,7 +35,7 @@ def create(settings, params={})
 
       def create_unauth_xml_doc(settings, params)
 
-        time = Time.new().strftime("%Y-%m-%dT%H:%M:%S")
+        time = Time.now.utc.strftime("%Y-%m-%dT%H:%M:%SZ")
 
         request_doc = REXML::Document.new
         root = request_doc.add_element "samlp:LogoutRequest", { "xmlns:samlp" => "urn:oasis:names:tc:SAML:2.0:protocol" }