This doesn't work for developers, but I'm not totally sure what we should do here. The issue is that developers should have a way to automatically run & test without additional manual commands. At the moment, I have to download the command manually (via copy & paste of the url), and then run the server.

At a minimum, I think we should include downloading of the jar file, if it doesn't exist, but preferably automatically run the server as well. I think there's examples of this in Firefox unit test land if we need them.

In the interests of moving testing and this PR forward, I think I'd be willing to accept an additional make target for the download, with extension of the README.md documentation. Then we can separate out the user story for making the selenium server run automatically.