provide a way to opt out of spec dependencies

[justin-roche]

I am trying to streamline an application and noticed in the shadow-cljs build report that kee-frame is relying on some heavy spec dependencies. I've been able to overwrite expound with a stub namespace by just adding an expound directory with a basic expound.alpha namespace, but that seems kind of hacky. Now I would like to avoid using spec as well. Would it be feasible to provide some kind of option to avoid using these or use them only in development?