Yahoo adds new social features to its renamed mobile app

SAN FRANCISCO - Yahoo has overhauled its main app for smartphones and tablets by emphasizing "social" features aimed at people who like to share and chat about news topics online.The revamped Yahoo app, now called Yahoo Newsroom, will augment its general news feed with more than 200 specialized channels that users can choose to follow on particular topics - such as a favorite celebrity, a political issue of interest or a breaking news event. The format encourages users to post comments on news i