The blockchain project’s cofounder Vitalik Buterin says its recent big upgrade lays a path for more technical changes, and greater adoption.LATE IN THE day on September 14 and into the early hours of the following morning, Vitalik Buterin and a few dozen crypto developers crowded into an office space in Berlin to flip the switch on the Merge. There wasn’t a literal switch to flip: Buterin, the 28-year-old Ethereum cofounder who has been active in cryptocurrency since his teens, had long ago envi