skip_before_filter登录跳过验证必备
http://guides.rubyonrails.org/v3.0.8/action_controller_overview.html#filters (例子来源)
http://apidock.com/rails/v3.0.5/AbstractController/Callbacks/ClassMethods/skip_filter
http://apidock.com/rails/ActionController/Filters/ClassMethods/skip_before_filter
官方文档给出的例子
class LoginsController < ApplicationController skip_before_filter :require_login, :only => [:new, :create] end