ATT is smart enough to know that mobile applications are becoming increasingly bandwidth-hungry and that means more of its subscribers may be at risk of going over their monthly data limits. With this in mind, ATT is taking the proactive step of encouraging app developers to make their applications use less data. Re/code notes that ATT last week handed out fliers to developers who attended its CES developers’ summit that gave tips for making apps that use data more efficiently and thus pose less of a risk when it comes to draining users’ monthly data supply. Among other things, ATT says developers should compress their images and text files, cache their content and avoid using redirects. The carrier is also