perf: distrubute smaller bundled code and include es2015 bundle

TypeScript compiler will now build to ES2015 code and modules. Babili is used to minify ES2015
code, providing an initial optimization that we couldn't previously get just from Uglify. Uses
Babel to convert ES2015 to UMD/ES5 code, and Uglify to minimize the output.

modules/@angular/platform-browser/index.ts

@@ -6,10 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-/**
- * @module
- * @description
- * Entry point for all public APIs of the platform-browser package.
- */
-export * from './src/platform-browser';
-// This file only reexports content of the `src` folder. Keep it that way.
+// This file is not used to build this module. It is only used during editing
+// by the TypeScript language service and during build for verification. `ngc`
+// replaces this file with production index.ts when it rewrites private symbol
+// names.
+
+export * from './public_api';