Tanganyika (pop. 9,560,000), where Stanley met Livingstone and Hemingway found Kilimanjaro, became a republic this week. For five days, the prancing crowds in Dar es Salaam celebrated the event, shrilling their approval of the fresh daubed letters "JT" (for Jamhuri Tanganyika, Republic of Tanganyika) on banners hung throughout the city. The rest of the world could also celebrate, for leader of the proud new republic would be Julius Nyerere, 40, a sensible, spindly onetime schoolteacher, who listens to the raucous cries of "Uhuru" (freedom) from the fiery nationalists of Africa, then puts his personal addendum on the slogan: "Uhuru...