Add js global classes to be injected in the vm context

Hi!

I had a problem with some code on the repl calling the node core api
https://groups.google.com/d/msg/clojurescript/znsyTrAyplw/5J_NY0uo8oUJ

It would appear that the JS classes like Error (and I guess it happens the same with Array, Object, etc.) are different in the vm and in the node core context, so when getting results from core apis like fs the constructors aren't the same leading to some problems in clojurescript where those are checked/used (instance? type and the js->clj functions).

Example:
```clojure
(let [fs (js/require "fs")]
  (.readFile fs "asdf asdf"
             (fn [err data]
               (println "err: " err)
               (println "type: "(type err))
               (println "instance?: "(instance? js/Error err)))))
;> err:  #<Error: ENOENT, open 'asdf asdf'>nil
;> type:  #<function Error() { [native code] }>
;> instance?:  false
```
(The last false should be true?)

A solution proposed by David would be to inject also those classes into the vm's context in here:
https://github.com/bodil/cljs-noderepl/blob/master/cljs-noderepl/src/cljs/repl/node_repl.js#L7

So I've added them to contextProperties:

I've taken into account the line that checks `hasOwnProperty`, I've tried it on the repl and it seems that even those properties are not listed when printing the object they are actually there (so all good):
```clojure
ClojureScript:cljs.user> (def ps [  "Array", "ArrayBuffer", "Boolean", "Buffer", "DataView", "Date", "Error",
  "EvalError", "Float32Array", "Float64Array", "Function", "Infinity",
  "Int16Array", "Int32Array", "Int8Array", "NaN" "Number", "Object",
  "RangeError", "ReferenceError", "RegExp", "String", "SyntaxError",
  "TypeError", "URIError", "Uint16Array", "Uint32Array", "Uint8Array",
  "Uint8ClampedArray", "clearInterval", "clearTimeout", "console", "process",
  "require", "setInterval", "setTimeout"])
ClojureScript:cljs.user> (every? #(.hasOwnProperty js/global %) ps)
true
```

I've tried using checkouts in a local example repo after doing `lein install` in my fork, but I'm not sure if I'm using the modified version and in the repl I get the same (incorrect) behavior... 

I'm a super noob so If you could point me to how to check it myself or check if the behavior is corrected it would be great.

Cheers