custom avatar support

app/models/upload.rb

@@ -31,11 +31,15 @@ class Upload < ActiveRecord::Base
 
   def destroy
     Upload.transaction do
-      Discourse.store.remove_file(url)
+      Discourse.store.remove_upload(self)
       super
     end
   end
 
+  def extension
+    File.extname(original_filename)
+  end
+
   def self.create_for(user_id, file, filesize)
     # compute the sha
     sha1 = Digest::SHA1.file(file.tempfile).hexdigest