title: Webpack imported class from module is not a constructor
body: <p>I have an angular2 package library ( call it A) that I import from another different angular2 project ( call it B ) using npm install .<br>
  All services , components from A seems to work on the B project , they are well imported injected and used .<br>
  But , only simple class definitions doesn't work . i.e I have a class defined as follow </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>export class JustAClass{
      public Title:string;
      constructor(title:string){
          this.Title = title;
      }
  
      getTitleLong():string{
          return 'Long '+this.Title;
      }
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p>and in the index.d.ts I export it . </p>
  
  <blockquote>
    <p>export { JustAClass } from './components/test/just';</p>
  </blockquote>
  
  <p>At project B I can see the just.d.ts file as follow :</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>export declare class JustAClass {
      Title: string;
      constructor(title: string);
      getTitleLong(): any;
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p>I work with webswtorm , when I use this class inside a file of project B it gives me intellisence and knows to point me to file definition  :</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>import { JustAClass } from 'my-project-lib-A';
  
  @Component({
      templateUrl: 'orders.html'
  })
  export class SomePage {
      
  
      constructor() {
  
          var d = new JustAClass('aaaa'); // this is undefiend in run time
          console.log(d.getTitleLong());
  
      }</code></pre>
  </div>
  </div>
  </p>
  
  <p>I get it 'JustAClass' undefined , and webpack throws an error :</p>
  
  <blockquote>
    <p><strong>WEBPACK_IMPORTED_MODULE_2_my-project-lib-A</strong>.JustAClass is not a constructor      </p>
  </blockquote>
  
  <p>I'm using ionic2 as project B if it matters . </p>