title: ngClass interpolation not working
body: <p>Consider the following icon-component. Why does the <code>color</code> variable remains as the word color instead of getting interpolated?</p>
  
  <pre><code>import {Component, Input, OnInit} from '@angular/core';
  
  @Component({
    moduleId: module.id,
    selector: 'nui-icon',
    template: `
      &lt;i class="material-icons" 
         [ngClass]="{color: true, 'bordered': border}"
         [ngStyle]="{'font-size':size + 'px'}"&gt;
        &lt;ng-content&gt;&lt;/ng-content&gt;
      &lt;/i&gt;
    `,
    styles: [`
      i {
        display: inline-flex;
      }
      i.bordered {
        border: 1px solid #d8d8d8;
        border-radius: 50%;
        padding: 15px;
      }
    `]
  })
  
  export class NuiIconComponent implements OnInit {
    @Input() color: string;
    @Input() size: string = '24';
    @Input() border: boolean = false;
  
    constructor () {}
  
    ngOnInit () {
    }
  }
  </code></pre>