Add filename extension to paperclip (#1718)

config/initializers/paperclip.rb

@@ -4,7 +4,7 @@ Paperclip.options[:read_timeout] = 60
 
 Paperclip.interpolates :filename do |attachment, style|
   return attachment.original_filename if style == :original
-  [basename(attachment, style), extension(attachment, style)].delete_if(&:empty?).join('.')
+  [basename(attachment, style), content_type_extension(attachment, style)].delete_if(&:empty?).join('.')
 end
 
 if ENV['S3_ENABLED'] == 'true'