refactor(forms): made directive names consistent

modules/angular2/forms.ts

@@ -16,7 +16,7 @@
 export * from './src/forms/model';
 export * from './src/forms/directives';
 export * from './src/forms/validators';
-export * from './src/forms/validator_directives';
+export * from './src/forms/directives/validators';
 export * from './src/forms/form_builder';
 
 import {FormBuilder} from './src/forms/form_builder';