title: Getting an error from console when using mdIcon
body: <p>Angular is throwing an error when I'm using mdIcon. Below is the code:</p>
  
  <pre><code>import {Component} from '@angular/core';
  import {MdIcon} from '@angular2-material/icon';
  @Component({
      selector: 'my-app',
      template: `
      &lt;md-toolbar&gt;
        &lt;md-icon class="demo-toolbar-icon"&gt;menu&lt;/md-icon&gt;
        &lt;span&gt;Default Toolbar&lt;/span&gt;
  
        &lt;span class="demo-fill-remaining"&gt;&lt;/span&gt;
  
        &lt;md-icon&gt;code&lt;/md-icon&gt;
      &lt;/md-toolbar&gt;`,
      directives: [MdIcon,MdToolbar],
  
  })
  export class AppComponent {} 
  </code></pre>
  
  <p>Error:</p>
  
  <blockquote>
    <p>ORIGINAL EXCEPTION: No provider for MdIconRegistry!
    Error: DI Exception
            at NoProviderError.BaseException [as constructor] (exceptions.ts:14)
            at NoProviderError.AbstractProviderError [as constructor] (reflective_exceptions.ts:53)
            at new NoProviderError (reflective_exceptions.ts:85)
            at ReflectiveInjector_._throwOrNull (reflective_injector.ts:844)
            at ReflectiveInjector_._getByKeyDefault (reflective_injector.ts:873)
            at ReflectiveInjector_._getByKey (reflective_injector.ts:835)
            at ReflectiveInjector_.get (reflective_injector.ts:632)
            at ElementInjector.get (element_injector.ts:19)
            at DebugAppView._View_AppComponent0.createInternal (AppComponent.template.js:141)
            at DebugAppView.AppView.create (view.ts:110)</p>
  </blockquote>
  
  <p>Can anyone please help me what i'm doing wrong here?</p>