chore(ts): duplicate the .es6 files in the facade directory to TypeScript.

Adds a gulp task which builds the .ts files (in the cjs build only).
The new files have extension .ts since they are now valid typescript.
Unfortunately until Typescript can emit System.require, we have to keep the old .es6 version
so traceur works inside the Karma preprocessor. This should be fixed soon.

modules/angular2/src/facade/browser.ts

@@ -0,0 +1,14 @@
+/**
+ * JS version of browser APIs. This library can only run in the browser.
+ */
+// HACK: workaround for Traceur behavior.
+// It expects all transpiled modules to contain this marker.
+// TODO: remove this when we no longer use traceur
+export var __esModule = true;
+
+var win = window;
+
+export {win as window};
+export var document = window.document;
+export var location = window.location;
+export var gc = window.gc ? () => window.gc() : () => null;