Michelle Curtis has rated Google searches professionally for eight years — training, testing and evaluating the algorithms for the company’s dominant search engine — while making $13. Raters who belong to the union joined union leaders Wednesday in delivering a petition to Google headquarters containing their demands, which include a request for a meeting between the union and Prabhakar Raghavan, a senior vice president at Google. “These workers are fighting this rip-off work structure all over the place