Twitter—the online platform that schooled us all on the art of brevity—has acquired a shiny new tool that seems tailor-made for marketers. In March, the social giant bought live-streaming video app Periscope, which marries the immediacy of Snapchat with the robust social sharing of Facebook. We asked social media experts to weigh in on the very visual platform—and share their thoughts on how retailers and brands can harness the power of Periscope.  How It Works Periscope streams live video. It’s watchable at the moment it’s being captured, and then for only 24 hours after