Peter Costanzo is the man who helped turn Donald Trump into @RealDonaldTrump. That, of course, is Trump’s Twitter account — a high-octane portal for the presumptive Republican presidential nominee to pump out insults, political attacks and self-promotion to more than 8 million followers. But the billionaire’s foray into the world of social media began with a much simpler purpose, yet one that’s still distinctively Trump: making money. Costanzo crossed paths with Trump in 2009 when he was working as online marketing director for the publishing company putting out the businessman’s book, “Think Like a Champion.” Twitter was still in its...