Not everyone can have the write stuff...The just-delivered June 15 issue of The Nation includes a wonderful obituary of San Francisco epistolist Cy Shain, who, as an octogenarian, mastered the prose form of the New York Times letters page."Shain, who held a variety of government posts in judicial education and prison reform in California, managed to crack the code, and how," writes The Nation's David Margolick, who notes that Shain managed to appear on the Times' letters page 39 times during th