title: OrderBy pipe issue
body: <p>I'm not able to translate this code from Angualr 1 to Angular 2:</p>
  
  
  
  <pre class="lang-html prettyprint-override"><code>ng-repeat="todo in todos | orderBy: 'completed'"
  </code></pre>
  
  <p>This is what i've done following the Thierry Templier's answer:</p>
  
  <p><strong>Component  template:</strong></p>
  
  
  
  <pre class="lang-html prettyprint-override"><code>*ngFor="#todo of todos | sort"
  </code></pre>
  
  <p><strong>Component code:</strong></p>
  
  
  
  <pre class="lang-js prettyprint-override"><code>@Component({
      selector: 'my-app',
      templateUrl: "./app/todo-list.component.html",
      providers: [TodoService],
      pipes: [ TodosSortPipe ]
  
  })
  </code></pre>
  
  <p><strong>Pipe code:</strong></p>
  
  
  
  <pre class="lang-js prettyprint-override"><code>import { Pipe } from "angular2/core";
  import {Todo} from './todo';
  
  @Pipe({
    name: "sort"
  })
  export class TodosSortPipe {
    transform(array: Array&lt;Todo&gt;, args: string): Array&lt;Todo&gt; {
      array.sort((a: any, b: any) =&gt; {
        if (a &lt; b) {
          return -1;
        } else if (a &gt; b) {
          return 1;
        } else {
          return 0;
        }
      });
      return array;
    }
  }
  </code></pre>
  
  <p>I'm trying to sort an array of <code>Todo</code>s, ordered by the property <code>completed</code>. First <code>todo.completed = false</code> and then the <code>todo.complete = true</code>.</p>
  
  <p>I don't understand very well the <code>transform</code> method and how to pass the arguments in that method and in the <code>sort</code> method.</p>
  
  <p>What is the <code>args: string</code> argument? What are <code>a</code> and <code>b</code> and where they come from?</p>