compitition
Dragonflyを推薦
http://stackoverflow.com/questions/6097302/carrierwave-or-paperclip-as-uploader
Carrierwaveを推薦
http://stackoverflow.com/questions/7419731/rails-3-paperclip-vs-carrierwave-vs-dragonfly-vs-attachment-fu
Carrierwaveを推薦.しかし、NewcomerとしてDragonflyを紹介
http://bcjordan.github.com/posts/rails-image-uploading-framework-comparison/
Paperclip
http://docs.komagata.org/3880
Carriewave
http://ja.asciicasts.com/episodes/253-carrierwave-file-uploads
Dragonfly
https://github.com/markevans/dragonfly