As online advertising continues to grow exponentially—digital advertisers will outspend TV advertisers by an estimated $40 billion this year—Chicago startup Popular Pays is making it easier for brands to find and work with social media influencers. And it just raised a new round of funding to help more agencies license its platform. Popular Pays announced Tuesday that it has raised a $5.5 million Series B led by Michigan-based Beringea. Silicon Valley firm GoAhead VC and Chic