docs(CORE_DIRECTIVES): improve docs for CORE_DIRECTIVES

Closes #4310

modules/angular2/src/core/directives.ts

@@ -22,16 +22,19 @@ export * from './directives/observable_list_diff';
 
 
 /**
- * A collection of the Angular core directives that are likely to be used in each and every Angular
+ * A collection of Angular core directives that are likely to be used in each and every Angular
  * application.
  *
- * This collection can be used to quickly enumerate all the built-in directives in the `@View`
+ * This collection can be used to quickly enumerate all the built-in directives in the `directives`
- * annotation. For example,
+ * property of the `@View` annotation.
- * instead of writing:
  *
- * ```
+ * ### Example ([live demo](http://plnkr.co/edit/yakGwpCdUkg0qfzX5m8g?p=preview))
+ *
+ * Instead of writing:
+ *
+ * ```typescript
  * import {NgClass, NgIf, NgFor, NgSwitch, NgSwitchWhen, NgSwitchDefault} from 'angular2/angular2';
- * import {OtherDirective} from 'myDirectives';
+ * import {OtherDirective} from './myDirectives';
  *
  * @Component({
  *  selector: 'my-component'
@@ -46,9 +49,9 @@ export * from './directives/observable_list_diff';
  * ```
  * one could import all the core directives at once:
  *
- * ```
+ * ```typescript
  * import {CORE_DIRECTIVES} from 'angular2/angular2';
- * import {OtherDirective} from 'myDirectives';
+ * import {OtherDirective} from './myDirectives';
  *
  * @Component({
  *  selector: 'my-component'
@@ -61,7 +64,6 @@ export * from './directives/observable_list_diff';
  *   ...
  * }
  * ```
- *
  */
 export const CORE_DIRECTIVES: Type[] = CONST_EXPR(
     [NgClass, NgFor, NgIf, NgNonBindable, NgStyle, NgSwitch, NgSwitchWhen, NgSwitchDefault]);