feat(animate): adds basic support for CSS animations on enter and leave

Closes #3876

modules/angular2/animate.ts

@@ -0,0 +1,5 @@
+export {Animation} from './src/animate/animation';
+export {AnimationBuilder} from './src/animate/animation_builder';
+export {BrowserDetails} from './src/animate/browser_details';
+export {CssAnimationBuilder} from './src/animate/css_animation_builder';
+export {CssAnimationOptions} from './src/animate/css_animation_options';