add Auth example, work around package controllers object issue

Hi, I was trying to create a page that required authentication (using Auth from BaseActions), and I ran into a problem with the controllers package object.  At runtime, when something tries to reference the controllers.FLASH_* constants, I get a NoSuchMethodError.  I believe that's due to
https://github.com/playframework/playframework/issues/1412
so I added a work around in this commit.

I'm totally new to scala and play, so I may not have done things in an idiomatic way; I'd appreciate any feedback you have about the "right way" to create a page that only authenticated users can see using play20-rememberme.  Or any other scala/play style or correctness issues.