fix attachment classes name

app/builders/builder.rb

@@ -33,7 +33,7 @@ class Builder
   def self.cache_key(rid, last_modified)
     last_modified = Time.at(0).to_s if last_modified.nil?
 
-    rid + '/' + last_modified
+    "#{rid}/#{last_modified}"
   end
 
 end

app/models/learning_object/attachment.rb

-module LearningObject
-  class Attachment
-    include ActiveModel::Model
+class LearningObject::Attachment
+  include ActiveModel::Model
 
-    #this attributes mirror Dspace bitstream values
-    attr_accessor :id, :name, :link, :retrieve_link, :description, :format, :mime_type, :size
-  end
+  #this attributes mirror Dspace bitstream values
+  attr_accessor :id, :name, :link, :retrieve_link, :description, :format, :mime_type, :size
 end