title: Angular 2 binding only refresh on Observable timer
body: <p>I'm trying to learn angular 2 and I've a conflict between Observable and angular's binding.The result of my binding works but only refresh on the timer.</p>
  
  <p>The timer is used in an header module to change title showed every 4 seconds based on an array :</p>
  
  <p>header.component.js</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>ngOnInit() {
    let timer = Observable.timer(4000,4000);
    timer.subscribe(t=&gt;this.currentTitle=(this.currentTitle===this.headerTitle.length-1)?0:++this.currentTitle);
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p>it runs as expected but when i create a second module with this template</p>
  
  <p>calculator.component.html :</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div&gt;
    &lt;input type="text" #value1/&gt;
    &lt;input type="text" #value2/&gt;
  
    &lt;p&gt;{{value1.value*value2.value}}&lt;/p&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>it works also but only every 4 seconds when the title change, why does observable timer affects my binding?</p>