Ignore exceptions clearing sessions

Rails 3 sessions can't be loaded by rails 4 but reset_session also
fails because it tries to clear the session, which tries to load it
in to clear it.

So monkey patch the session to ignore exceptions during clear so
that out normal reset-on-exception logic will reset the session.

config/initializers/session.rb

@@ -0,0 +1,13 @@
+module ActionDispatch
+  class Request < Rack::Request
+    class Session
+      def clear_with_rescue
+        clear_without_rescue
+      rescue
+        # lets not worry about it...
+      end
+
+      alias_method_chain :clear, :rescue
+    end
+  end
+end