Document that Aero needs to be a dependency and how to include it

[arichiardi]

I was trying mach target from the repo but it fails:

#error {:message No such namespace: aero.core, could not locate aero/core.cljs, aero/core.cljc, or Closure namespace "aero.core", :data {:tag :cljs/analysis-error}}

Probably now that the dependency is gone there will need to be a way to import it from clojars.

Thanks folks for this tool, I am going to experiment with it (on the previous tag) :smile:

[jonpither]

Fixed by #12