TUNIS - Tunisians Saturday marked the first anniversary of the revolution that started the "Arab Spring" with celebrations that were true to the spirit of the revolt: raucous, unscripted, and driven by the energy of ordinary people. Thousands of people flooded into Bourguiba Avenue in the center of the capital, the same spot where demonstrators massed exactly one year ago, forcing autocratic leader Zine al-Abidine Ben Ali to accept his rule was over and flee the country. Since that moment, Tunisia has become a model for democratic change in the Middle East.