Benchmark against Z.lua

[euank]

From https://github.com/skywind3000/z.lua#features

10x times faster than fasd and autojump, 3x times faster than z.sh.

The methodology is mentioned in the readme, and doesn't look super scientific. I think we can get a better number and see how it stacks up against pazi with our benchmark harness.

It could be worth taking some ideas too :)