code: def quality(mime_type, ranges)
      parsed_ranges = ranges.split(",").map { |r| parse_media_range(r) }
      quality_parsed(mime_type, parsed_ranges)
    end
docs: Returns the quality "q" of a mime_type when compared against
    the media-ranges in ranges. For example:
  
       irb> quality("text/html", "text/*;q=0.3, text/html;q=0.7, text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5")
       => 0.7