PHOENIX — The slump began in the spring and lingered deep into summer, but Carlos Gonzalez never lost faith in himself, nor in his ability to help carry the Rockies toward the playoffs. All he needed, he kept insisting, was time to iron out some mechanical flaws in pretty swing. It took longer than anyone thought, but CarGo has returned. Gonzalez mashed a pair of two-run home runs Tuesday night, powering the Rockies to a 4-2 victory over Arizona at Chase Field.