Ensure that if a different user signs in to LP it is reflected in community

We now record the user id from the warden cookie in the discourse session.  This allows to easily check on every request if the user id has changed, and if so, to do the dance.  Removed all the noonce stuff because it was never being set and was a holdover from the OAuth days.
Clean up comment
Merge pull request #23 from LessonPlanet/jr/ensure-synced-user

Ensure that if a different user signs in to LP it is reflected in commun...