Inspector - cljs compatibility

I wonder what it would take to make the Inspector cljs-compatible.

Fortunatlely, cider and cider-nrepl's code appears to be a 'thin client' for all things Inspector, so the bulk of the changes would reside here.

Probably, it would be best to handle cljs values as strings (i.e. we don't try to `read` them into JVM clojure).