update README.md

README.md

 # Paperclip::Qiniu
 
-TODO: Write a gem description
-
-## Installation
-
-Add this line to your application's Gemfile:
-
-    gem 'paperclip-qiniu'
-
-And then execute:
-
-    $ bundle
-
-Or install it yourself as:
-
-    $ gem install paperclip-qiniu
+storage paperclip attachments to http://qiniutek.com
 
 ## Usage
 
-TODO: Write usage instructions here
+0. confirm you are working on a rails app
+
+1. add following line to `Gemfile`
+
+```
+gem 'paperclip'
+gem 'paperclip-qiniu'
+```
+
+2. edit your `config/application.rb`
+
+```
+module PaperclipQiniuExample
+  class Application < Rails::Application
+    # ....
+    config.paperclip_defaults = {:storage => :qiniu,
+      :qiniu_credentials => {
+        :access_key => ENV['QINIU_ACCESS_KEY'] || raise("set env QINIU_ACCESS_KEY"),
+        :secret_key => ENV['QINIU_SECRET_KEY'] || raise("set env QINIU_SECRET_KEY")
+      },
+      :bucket => "paperclip-qiniu-example",
+      :use_timestamp => false
+    }
+  end
+end
+```
+
+3. add a model like this
+
+```
+class Image < ActiveRecord::Base
+  attr_accessible :file
+  has_attached_file :file, :styles => { :medium => "300x300>", :thumb => "100x100>" }
+  validates :file, :attachment_presence => true
+end
+```
 
 ## Contributing