Syrians danced jubilantly in the streets and fired celebratory shots into the air Sunday after dictator Bashar Assad fled the country and acceded to a peaceful transition of power after Islamist insurgents took control of the capital of Damascus and ended his family's half-century reign. The stunning fall of the Assad regime, which used chemical weapons on its own people and was backed by Iran, left large question about what happens next in Syria and the larger Middle East already gripped...