feat(forms): add support for validations

modules/angular2/src/forms/validator_directives.js

@@ -0,0 +1,15 @@
+import {isBlank, isPresent} from 'angular2/src/facade/lang';
+import {List, ListWrapper, StringMapWrapper} from 'angular2/src/facade/collection';
+import {Decorator} from 'angular2/core';
+
+import {ControlGroup, Control, ControlDirective} from 'angular2/forms';
+import * as validators from 'angular2/forms';
+
+@Decorator({
+  selector: '[required]'
+})
+export class RequiredValidatorDirective {
+  constructor(c:ControlDirective) {
+    c.validator = validators.compose([c.validator, validators.required]);
+  }
+}