Rolling Stones guitarist Keith Richards had a hot time on Martha’s Vineyard Saturday night. Keef, who’s been an occasional visitor to the Vineyard for years, was at the Edgartown restaurant-bar Atria, where he watched fire spinner Martina Fajkusova do her thing. (Just like it sounds, fire spinning involves spinning objects - chains, batons, and hula hoops - that are on fire.) The man who has seen it all was mighty impressed, at least according to the fire spinner’s father. “[Richards] was quite taken with the performance,’’ Jib Ellis told us yesterday. The Czech-born Fajkusova, who lives in Oak Bluffs and also surfs, had another famous fan in the audience: Adam Sandler.