Chrome 59 gets cross-platform Headless mode support. Chrome Headless is already available on Linux so you could start hacking with it right now, even if you're not on Linux. The only thing you will need is Docker.
For now, there is one example of use in this repository – capturing screenshots for different platforms (Desktop, Mobile & Tablet) using Headless Chrome. But more may appear later, contributions are always welcome.
You could read Chrome announcement post for more generic use cases on Headless mode.
# Clone Github repository
$ git clone [email protected]:asyne/mindless.git
# Build Docker image
$ cd mindless/
$ docker build -t mindless .
# Run Docker container and take screenshots of Github's main page
# «output» folder will be created in the current directory
$ docker run -it --cap-add=SYS_ADMIN -v $(pwd)/output:/output mindless --url https://github.com/