Important new entry in the README

so I've got a suite of acceptance tests, that are agnostic to which of the various backends is in use.

I wanted to use :bindings to set a value differently for each suite

but that's top-level, it seems, and can't be set per-suite. I'm currently falling back to using command line parameters passed by my deps.edn commands. that's a long way from ideal, though, so I'm open to suggestions for other ways to run a suite of tests while setting a different option.