The Hamptons’ summer art fair season got off to a roaring start last night with the opening of ArtHamptons and Art Market Hamptons, both open through July 13. Despite the bumper-to-bumper traffic piling up en route to both events last night, the fairs had a less frenzied, more sociable vibe compared to the crazed hustle of New York City’s Frieze and Armory weeks.