chore(build): don’t include export var __esModule = true in every file

But do it during the build process for cjs.
Right now we only need this when we transpile from ts
directly to es5. This is only the case in our
cis build, as for our browser build we only transpile
from ts to es6 via ts and then use traceur to do
the rest.

modules/angular2/src/core/zone/ng_zone.ts

@@ -32,7 +32,7 @@ export class NgZone {
   //   zone.run(() => {});    // nested call -> in-turn
   // });
   _nestedRun: number;
-  
+
   // TODO(vicb): implement this class properly for node.js environment
   // This disabled flag is only here to please cjs tests
   _disabled: boolean;
@@ -54,7 +54,7 @@ export class NgZone {
     this._pendingMicrotasks = 0;
     this._hasExecutedCodeInInnerZone = false;
     this._nestedRun = 0;
-    
+
     if (global.zone) {
       this._disabled = false;
       this._mountZone = global.zone;
@@ -99,11 +99,11 @@ export class NgZone {
    * });
    * ```
    */
-  run(fn) { 
+  run(fn) {
     if (this._disabled) {
       return fn();
     } else {
-      return this._innerZone.run(fn);     
+      return this._innerZone.run(fn);
     }
   }
 
@@ -123,12 +123,12 @@ export class NgZone {
    * });
    * ```
    */
-  runOutsideAngular(fn) { 
+  runOutsideAngular(fn) {
     if (this._disabled) {
       return fn();
     } else {
       return this._mountZone.run(fn);
-    } 
+    }
   }
 
   _createInnerZone(zone, enableLongStackTrace) {