z is the new j

First, there was [j](http://github.com/rupa/j/).

Then, there was [j2](http://github.com/rupa/j2/), with some python added. Made
it easier to experiment with some stuff I'd been thinking about.

Now there's this, where I rewrote j2 back in bash. I like it. Sorry about all
the repos , but it kind of grew this way.