phantomjs 1.9.8 cannot be run on macOS Sierra

[boneskull]

See ariya/phantomjs#14558.

We need to use 1.9.8 in CI to ensure compatibility, so upgrading is not yet on the table (unless we can get some numbers around 1.9.x's popularity).

My proposed workaround is to add karma-chrome-launcher and use that instead if the browser suite is running on Sierra. It's better than nothing. 😝