Sometimes, the only place to start is at the beginning. In early January 2010, a large manilla envelope came to me in the mail from the federal prison in Fort Worth. A reader commented on a story I had written for The Dallas Morning News about the Posse's very first barbecue tour, to the Central Texas BBQ heartland. "It's all good," the reader wrote. "'But' have you really tasted the best barbecue in Texas?" The reader said his name was Clyde Biggins and that he once owned "Clyde's Old Fashion Hickory Smoked Barbecue" on Westmoreland Road in Dallas. "'Note,'" Biggins…