refactor(Lifecycle hooks): move the hooks to their own module (lifecycle_hooks)

BREAKING CHANGE

Lifecycle hooks now live in the `angular2/lifecycle_hooks` module.
They previously lived in the `metadata` module.

modules/angular2/angular2.ts

@@ -15,3 +15,4 @@ export * from './forms';
 export * from './render';
 export * from './profile';
 export {bootstrap} from 'angular2/src/core/application';
+export * from './lifecycle_hooks';