Libraries around the country are falling victim to the weak economy. Suffering from budget cuts, many are in danger of closing. But in Louisville, Kentucky, the public library system is growing.   Its director, Craig Buthod, has reinvented the libraries into community education centers for all generations and developed a program that combines student IDs, bus tickets and library cards, getting Louisville kids to check out 3,000 books a day. We talk with Buthod, 2010 Librarian of the Year, about the future of libraries in the digital age.