Fix duplicate flash error message caused by devise timeout

Previously, if you revisited Bridge Troll after having timed out, you would
see one error saying 'Your session expired' and another saying 'true'.

Devise inserts a :timedout key into the FlashHash, which careful programmers
have to avoid. See https://github.com/plataformatec/devise/issues/1777

Also: pasting over the latest Devise en.yml for fun.