yt_find.rb

    # Finds videos by tags (keywords).
    # 
    # You can use the operators +NOT+(-) and +OR+(|). For example:
    #   find_by_tag('cats|dogs', '-rats')
    def find_by_tag(*tags)
      url = "videos/-/%7Bhttp%3A%2F%2Fgdata.youtube.com%2Fschemas%2F2007%2Fkeywords.cat%7D"
      keywords = tags.map{ |t| CGI::escape(t) }.join('/')
      request("#{url}#{keywords}")
    end