How about nightmare headless browser integration

[focusaurus]

Just wanted to file an issue to see if others might be interested in adding support for zuul running the nightmare electron-based (optionally) headless browser. I just learned about nightmare moments ago so apologies if I'm completely misunderstanding the situation, but I believe it would be a viable alternative to phantomjs. I would love to move away from the sadly under-supported phantomjs project. Please comment or react so we can gauge how much if any interest there is.