Fix IE8/IE9 bug that may cause hanging cross-domain requests.

See: http://stackoverflow.com/a/9928073/3949247

Author: asavoy

src/system.js

@@ -77,6 +77,10 @@
         xhr.onload = load;
         xhr.onerror = error;
         xhr.ontimeout = error;
+        // IE8/IE9 bug may hang requests unless all properties are defined. 
+        // See: http://stackoverflow.com/a/9928073/3949247
+        xhr.onprogress = function() {};
+        xhr.timeout = 0;
       }
       function load() {
         fulfill(xhr.responseText);
@@ -286,4 +290,4 @@
     if (curScript.getAttribute('data-init'))
       window[curScript.getAttribute('data-init')]();
   }
-})();
+})();