isPlainObject: by pass prototype check in nw.js environments

- to make sure that plotly.js is compatible with async
  request handles (e.g. lash)
- side effect: isPlainObject(new Constructor()) now returns true
  in nw.js

Author: etpinard

src/lib/is_plain_object.js

@@ -11,6 +11,15 @@
 
 // more info: http://stackoverflow.com/questions/18531624/isplainobject-thing
 module.exports = function isPlainObject(obj) {
+
+    // We need to be a little less strict in the `imagetest` container because
+    // of how async image requests are handled.
+    //
+    // N.B. isPlainObject(new Constructor()) will return true in `imagetest`
+    if(window && window.process && window.process.versions) {
+        return Object.prototype.toString.call(obj) === '[object Object]';
+    }
+
     return (
         Object.prototype.toString.call(obj) === '[object Object]' &&
         Object.getPrototypeOf(obj) === Object.prototype