Added a bit more to the session documentation on how to clear sessions

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@922 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/base.rb

@@ -96,16 +96,19 @@ class MissingFile < ActionControllerError #:nodoc:
   #
   # You can place objects in the session by using the <tt>@session</tt> hash:
   #
-  #   @session["person"] = Person.authenticate(user_name, password)
+  #   @session[:person] = Person.authenticate(user_name, password)
   #
   # And retrieved again through the same hash:
   #
-  #   Hello #{@session["person"]}
+  #   Hello #{@session[:person]}
   #
   # Any object can be placed in the session (as long as it can be Marshalled). But remember that 1000 active sessions each storing a
   # 50kb object could lead to a 50MB memory overhead. In other words, think carefully about size and caching before resorting to the use
   # of the session.
   #
+  # For removing objects from the session, you can either assign a single key to nil, like <tt>@session[:person] = nil</tt>, or you can
+  # remove the entire session with reset_session.
+  #
   # == Responses
   #
   # Each action results in a response, which holds the headers and document to be sent to the user's browser. The actual response