I rediscovered “The Country Bunny and the Little Gold shoes when my children were young - they loved it too - but I never wondered about the writer until recently, when I saw DuBose Heyward’s name in a newspaper story about the new production of “Porgy and Bess’’ now running on Broadway; and I realized that “Porgy’’ and “The Country Bunny’’ were created by the same person. Who was he? How did he come to write these two stories, so different, yet each, in its own way, enduring?