http://zool.iteye.com/blog/712836
http://www.cnblogs.com/chengguyun/archive/2011/07/26/2117756.html
目前版本还不适合使用rails_admin
将后台用rails_admin重建
http://www.hupengxing.com/blogs/87-%E5%B0%86%E5%90%8E%E5%8F%B0%E7%94%A8rails_admin%E9%87%8D%E5%BB%BA
undler could not find compatible versions for gem "rails":
In Gemfile:
rails (= 3.0.9)
rails_admin depends on
rails (3.1.0.rc6)