NAIROBI (Reuters) - Somalia has replaced Sudan as the "epicentre of jihadism" in east Africa since the rise of a powerful Islamist movement, according to a U.S. author who has just finished a new book on the Horn of Africa nation. "The most potent expression of jihadism in the region has occurred in stateless Somalia," says Gregory Alonso Pirio. His book, "The African Jihad: Bin Laden's Quest for the Horn of Africa", is due to be published early next year. "With the military triumph of the Islamic Courts, southern Somalia came to replace Sudan as the epicentre of jihadism in...