title: undefined method `stringify_keys'
body: <p>When I try to upload image using Paperclip gem I got this error:</p>
  
  <p>NoMethodError (undefined method `stringify_keys' for &lt;ActionDispatch::Http::UploadedFile:0x000000025387f0&gt;)</p>
  
  <pre><code>class MenuItem &lt; ActiveRecord::Base
   has_one :image
  
  
  end
  
  class Image &lt; ActiveRecord::Base
   belongs_to :menu_item
   has_attached_file :image, :styles =&gt; {
              :large =&gt; "640x480",
              :medium =&gt; "300x300", 
              :thumb =&gt; "100x100" 
             }
  end
  </code></pre>