参考：https://github.com/nowa/carrierwave-upyun

1. 在Gemfile中：

   gem 'carrierwave'
   gem 'carrierwave-upyun'
   

2. 在config/initializers/carrierwave.rb中，增加：

   CarrierWave.configure do |config|
   config.storage = :upyun
   config.upyun_username = "xxxxxx"
   config.upyun_password = 'xxxxxx'
   config.upyun_bucket = "my_bucket"
   config.upyun_bucket_host = "http://my_bucket.files.example.com"
   end
   

3. 在对应的uploader中, 使用 storage :upyun：

     class AvatarUploader < CarrierWave::Uploader::Base
       storage :upyun
     end