All but four homes on Nantucket are out of power as the Blizzard of 2015 hammers the island with 78 mph winds.“We have an entire Island-wide power outage,” Dave Fronzuto, head of Nantucket’s emergency management, told Boston Herald Radio’s “Morning Meeting” show today.He said the island has also lost “almost all of its cell phone coverage” and people are being evacuated to an emergency shelter.