Merge pull request #1169 from chadoh/patch-1

Add default_url option to Quick Start example

README.md

@@ -101,7 +101,7 @@ In your model:
 ```ruby
 class User < ActiveRecord::Base
   attr_accessible :avatar
-  has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "100x100>" }
+  has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "100x100>" }, :default_url => "/images/:style/missing.png"
 end
 ```