Joel Pavelski, 27, isn’t the first person who has lied to his boss to scam some time off work. But inventing a friend’s funeral, when in fact he was building a treehouse — then blogging and tweeting about it to be sure everyone at the office noticed? That feels new. Such was a recent management challenge at Mic, a five-year-old website in New York that is vying to become a leading news source created by and for millennials. Recent headlines include “Don’t Ban Muslims, Ban Hoverboards” and “When Men Draw Vaginas.”