title: Paperclip exception : Paperclip::AdapterRegistry::NoHandlerError
body: <p>Using Paperclip 3.0.1 in rails 3.2.2 I got this error:</p>
  
  <pre><code>**Paperclip::AdapterRegistry::NoHandlerError** 
  (No handler found for "2009-11-29-133527.jpg"):
  </code></pre>
  
  <p>In my model I have: </p>
  
  <pre><code>class Product &lt; ActiveRecord::Base
      ...
      has_many :assets 
      accepts_nested_attributes_for :assets
   end
  
   class Asset &lt; ActiveRecord::Base
       belongs_to :product
       has_attached_file :image,
                 :path =&gt; ":rails_root/public/system/:attachment/:id/:style/:filename",
                 :url =&gt; "/system/:attachment/:id/:style/:filename", 
                 :styles =&gt; { :medium =&gt; "300x300&gt;", :thumb =&gt; "100x100&gt;" }
    end
  </code></pre>
  
  <p>The exception is raised at:</p>
  
  <pre><code>def create
       **@product = Product.new params[:product]**
       ...
  end
  </code></pre>
  
  <p>with params: </p>
  
  <pre><code>{...,
   "product"=&gt;{"title"=&gt;"wibble1", 
               **"assets_attributes"=&gt;{"0"=&gt;{"image"=&gt;"2009-11-29-133527.jpg"}
                                    },** 
               "description"=&gt;"Who is wibble...", 
               "price"=&gt;"23.45"
              }, 
               "commit"=&gt;"Create Product", 
               ...}
  </code></pre>
  
  <p>Anyone know what's going on?</p>