KANSAS CITY, Mo. — The Yankees started the second month of the season the way they finished the first. And they ended the first day of May with the best record in baseball after rallying to beat the Royals, 6-4, at Kauffman Stadium on Sunday. The Yankees (16-6) swept the Royals (7-13) and have won a season-high nine straight games, the longest winning streak in the majors this season. They have swept their last three series and moved past the Mets for the best record in baseball. “I think the good thing is we’re doing a lot of things well to allow us to win games and we’re winning games in dif…