Snapchat and Twitter adopting new looks to gain more users

San Francisco • A pair of struggling social-media darlings have decided they need to take on new looks if they want to prosper.Twitter is rolling out a 280-character limit for nearly all its users, abandoning its iconic 140-character limit for tweets.And Snapchat, long an app popular with young people, will undergo a revamp to make itself easier to use, in the hopes it can attract a wider audience.Both companies announced the moves Tuesday as they look for ways to expand beyond their passio