Hi and welcome to Insider Advertising for May 24. I'm senior advertising reporter Lauren Johnson, and here's what's going on: Check out the PR firms challenging the giants.Meet David Zaslav.Marketing tech startup Key raises $3 million. If this email was forwarded to you, sign up here for your daily insider's guide to advertising and media. Tips, comments, suggestions? Drop me a line at LJohnson@insider.com or on Twitter at @LaurenJohnson. Barbara Bates, global CEO of Hotwire Hotwire 9 public relations companies are challenging the status quo and taking on giants like Edelman and BCWThe biggest public relations agencies are facing new