add back wikirate_tag.rb and 

1. add back wikirate_tag.rb
2. add default html tooltip for the clipboard
3. change readme from text to md format
4. add config file for link_thumbnailer to repo

again, this could be a little less dramatic without the bang.  Eg:

      c = Card.create :type_id=>Card::WikirateTagID, :name=>tag
      if c.errors.any?
        puts "invalid tag name: #{tag} FROM #{card.name}"
      end

just FYI.  no need to fix here.