def destroy
    self.set_session_current_user nil
    respond_to do |format|
      format.html { redirect_to session_url }
      format.json { head :no_content }
    end
  end
def destroy
    self.set_session_current_user nil
    respond_to do |format|
      format.html { redirect_to session_url }
      format.json { head :no_content }
    end
  end
DELETE /session