Added Facebook response redirect.

I tried the logout example with my facebook app and compared it to how I made with RestFb. The current logoutservlet isn't logging out correct.

The provided code is just an example. I haven't tried the exception for all cases.
siteurl.com could probably be replaced with request.getContextPath() but with logoutservlet removed at the end.

See this link for more information
http://stackoverflow.com/questions/2764436/facebook-oauth-logout