Although St. Barth has been known as a tropical playground for the rich and famous for several decades, it’s not so long ago that the Caribbean island was a scruffy, even rough corner of paradise attracting hard-living ex-pat dropouts who fancied themselves as modern pirates. If that sounds like a Jimmy Buffett song, that’s because the late musician was heavily influenced by that world after he moved to Saint Barthélemy in the 1970s. In an excerpt from his book “ Treasured Island: The Story of