[react-packager] Fix jest tests

jestSupport/env.js

@@ -0,0 +1,5 @@
+'use strict';
+
+global.setImmediate = global.setImmediate || function(fn) {
+  return setTimeout(fn, 0);
+};

jestSupport/scriptPreprocess.js

@@ -10,6 +10,10 @@ module.exports = {
   transformSource: transformSource,
 
   process: function(src, fileName) {
+    if (fileName.match(/node_modules/)) {
+      return src;
+    }
+
     try {
       return transformSource(src);
     } catch(e) {