fix(bundles): don't pre-append polyffils to angular2.js bundle

BREAKING CHANGE:

Previously `angular2.js`, `angular2.min.js` and `angular2.dev.js` bundles
would have zone.js and reflect-metadata pre-appended. New bundles don't
contain zone.js nor reflect-metadata - those external dependencies can
be easily loaded into a browser using `angular2-polyfills.js`

gulpfile.js

@@ -1154,7 +1154,7 @@ gulp.task('bundles.js.umd.min', ['!bundles.js.umd', '!bundle.ng.polyfills'], fun
 gulp.task('!bundle.js.prod.deps', ['!bundle.js.prod'], function() {
   var bundler = require('./tools/build/bundle');
 
-  return merge2(addDevDependencies('angular2.js'),
+  return merge2(bundler.modify(['dist/build/angular2.js'], 'angular2.js'),
                 bundler.modify(['dist/build/http.js'], 'http.js'),
                 bundler.modify(['dist/build/router.js'], 'router.js'))
       .pipe(gulp.dest('dist/js/bundle'));
@@ -1164,7 +1164,7 @@ gulp.task('!bundle.js.min.deps', ['!bundle.js.min'], function() {
   var bundler = require('./tools/build/bundle');
   var uglify = require('gulp-uglify');
 
-  return merge2(addDevDependencies('angular2.min.js'),
+  return merge2(bundler.modify(['dist/build/angular2.min.js'], 'angular2.min.js'),
                 bundler.modify(['dist/build/http.min.js'], 'http.min.js'),
                 bundler.modify(['dist/build/router.min.js'], 'router.min.js'))
       .pipe(uglify())
@@ -1207,7 +1207,7 @@ function addDevDependencies(outputFile) {
 gulp.task('!bundle.js.dev.deps', ['!bundle.js.dev'], function() {
   var bundler = require('./tools/build/bundle');
 
-  return merge2(addDevDependencies('angular2.dev.js'),
+  return merge2(bundler.modify(['dist/build/angular2.dev.js'], 'angular2.dev.js'),
                 bundler.modify(['dist/build/http.dev.js'], 'http.dev.js'),
                 bundler.modify(['dist/build/router.dev.js'], 'router.dev.js'))
       .pipe(gulp.dest('dist/js/bundle'));