Dan PrimackIllustration: Natalie Peeples/AxiosUnderdog, a Brooklyn-based fantasy sports and sports betting app, tells Axios that it raised $70 million in Series C funding at a $1.23 billion valuation from Spark Capital. It's the first close of a round that could total more than $100 million.Why it matters: Underdog co-founder and CEO Jeremy Levine sold prior startups to both DraftKings and the parent company of FanDuel, but recently told employees that he has no intention of "finishing third aga...