fix(test_lib): reexport fake_async via angular/test

previously fake_async was not being publically exported at all

modules/angular2/test.ts

@@ -9,4 +9,5 @@
 export * from './src/test_lib/test_lib';
 export * from './src/test_lib/test_component_builder';
 export * from './src/test_lib/test_injector';
+export * from './src/test_lib/fake_async';
 export * from './debug';