docs(core): add docs for PipeTransform interface

modules/angular2/src/core/change_detection/pipe_transform.ts

@@ -1,34 +1,36 @@
 /**
  * To create a Pipe, you must implement this interface.
  *
- * Angular invokes the `transform` method with the subject as the `value` argument and any
- * parameters in the `args` Array.
+ * Angular invokes the `transform` method with the value of a binding
+ * as the first argument, and any parameters as the second argument in list form.
  *
  * ## Syntax
  *
- * `subject | pipeName[:arg0[:arg1...]]`
+ * `value | pipeName[:arg0[:arg1...]]`
  *
  * ## Example
  *
- * The `RepeatPipe` below repeats the subject as many times as indicated by the first argument:
+ * The `RepeatPipe` below repeats the value as many times as indicated by the first argument:
  *
  * ```
+ * import {Pipe, PipeTransform} from 'angular2/angular2';
+ *
  * @Pipe({name: 'repeat'})
- * class RepeatPipe implements PipeTransform {
- *
- *  transform(value: any, args: any[] = []) {
- *    if (isBlank(args) || args.length == 0) {
- *      throw new BaseException('limitTo pipe requires one argument');
- *    }
- *
- *    let times: number = args[0];
- *
- *    return value.repeat(times);
- *  }
+ * export class RepeatPipe implements PipeTransform {
+ *   transform(value: any, args: any[] = []) {
+ *     if (args.length == 0) {
+ *       throw new Error('repeat pipe requires one argument');
+ *     }
+ *     let times: number = args[0];
+ *     return value.repeat(times);
+ *   }
  * }
  * ```
  *
  * Invoking `{{ 'ok' | repeat:3 }}` in a template produces `okokok`.
+ *
+ * See full working example: http://plnkr.co/edit/f5oyIked9M2cKzvZNKHV?p=preview
+ *
  */
 export interface PipeTransform { transform(value: any, args: any[]): any; }