chore(build): Upgrade to TypeScript@1.5.3

This change also makes us compliant with 1.6.0-dev compiler,
so we can do some experiments with apps that use 1.6 features
and compile against Angular.

We should probably add a travis build for 1.6 so we stay compatible
with both versions.

modules/angular2/src/test_lib/test_lib.ts

@@ -12,7 +12,9 @@ import {createTestInjector, FunctionWithParamTokens, inject} from './test_inject
 
 export {inject} from './test_injector';
 
-export function proxy() {}
+export function proxy(): ClassDecorator {
+  return (t) => t;
+}
 
 var _global: jasmine.GlobalPolluter = <any>(typeof window === 'undefined' ? global : window);