nailgun 0.9.1 (zombie formula)

As per #21880 nailgun was removed because it was woefully outdated and had moved to a new packaging format. This commit brings the nailgun formula back from the boneyard and updates it to 0.9.1.

I've also taken a stab at writing a test, but there's a few ways that it's not ideal. Just testing the ng command would miss testing the server, but there's no good way that I can see to spin up the ng-server without backgrounding the process and waiting for it to bind to its port.

Also, if there's a way to get an unassigned port from the ephemeral range in Ruby, I'd rather do that than hard code 8765, but I didn't find a simple way to pick an unused port. 
Ah, I understand now – neither is at all useful without the other, and both are explicitly designed to only be used on a single machine:

    Before you download it, be aware that *it's not secure*. Not even close. Although there are means to ensure that the client is connected to the server from the local machine, there is not yet any concept of a "user".

They're two separate binaries to solve one problem, but that's what the madness of JVM classloading drives us to, I suppose.