Rename random-guess to random-guess-needle.

Woah man do I need to figure out a way to compose these things better.
Well I got this thing to work. But I didn't like it.
Hopefully this test is a bit more robust now.

If this doesn't work I'll have to write a wait-for.
Better way to serialize vars

This way we don't have to cereal/defn, and can refer to 3rd-party vars
in the same way.