zbuf: cuz binary data in JS still sucks

jDataView *almost* makes it decent to use binary data buffers on both
node and the browser, but falls apart because:

1. browserify injects a Buffer that makes jDataView think it's running
   under node, but buffer-browserify is not fully functional.
2. jDataView has syntax errors and test failures when run under
   phantomjs.

So, here's zbuf in the meantime. Maybe the buffer story gets better in
the future and the wrapper seems a little silly.

But it lets me move on to useful code for now.