BOSTON — Since DeMarcus Cousins' return last week from a torn left Achilles tendon, Golden State has looked borderline unstoppable, which isn't necessarily surprising given that it boasts five All-Stars in their prime. But in their 115-111 win Saturday over the Celtics at TD Garden, the Warriors shed their air of invincibility — for one night, at least. Boston — the preseason Eastern Conference favorite —　weathered a slew of Golden State rallies, made timely second-half stops and nearly handed the Warriors their first defeat in more than three weeks. Not until Stephen Curry hit two free throws with 6.2 seconds left did Golden State finally seal its 10th straight victory.