made the logout url use ruby cas client helper methods rather than ma…

…nuall build

app/controllers/devise/cas_sessions_controller.rb

@@ -56,8 +56,8 @@ def destroy
     service_url = request.protocol
     service_url << request.host
     service_url << ":#{request.port.to_s}" unless request.port == 80
-    
-    redirect_to("#{::Devise.cas_client.logout_url(destination_url, follow_url)}=#{service_url}/users/service")
+
+    redirect_to(::Devise.cas_client.logout_url(destination_url, follow_url, ::Devise.cas_service_url(service_url, devise_mapping)))
   end
 
   def single_sign_out
@@ -114,6 +114,11 @@ def returning_from_cas?
     params[:ticket] || request.referer =~ /^#{::Devise.cas_client.cas_base_url}/ || request.referer =~ /^#{url_for :action => "service"}/
   end
 
+  def cas_logout_url
+    ::Devise.cas_client.add_service_to_login_url(::Devise.cas_service_url(request.url, devise_mapping))
+  end
+  helper_method :cas_login_url
+
   def cas_login_url
     ::Devise.cas_client.add_service_to_login_url(::Devise.cas_service_url(request.url, devise_mapping))
   end