Tunis (Reuters) - Tunisian troops clashed with Islamist militants near the border with Algeria on Tuesday, a security source said, in an area where the army is hunting al Qaeda-linked fighters. Tunisia, economically struggling and deeply polarized between Islamists and their opponents, is in the throes of a political transition that began with the overthrow of strongman Zine al-Abidine Ben Ali in a popular uprising two years ago. ...