title: Aurelia / ES6 class and property definition, plumber syntax error
body: <p>I am trying to get the getting started app of Aurelia to work, but I am getting an error right at the first page.
  <a href="http://aurelia.io/get-started.html" rel="nofollow">http://aurelia.io/get-started.html</a></p>
  
  <p>The code in question : </p>
  
  <pre><code>export class Welcome {
    heading = 'Welcome to the Aurelia Navigation App!';
    firstName = 'John';
    lastName = 'Doe';
  
    get fullName(){
      return `${this.firstName} ${this.lastName}`;
    }
  
    welcome(){
      alert(`Welcome, ${this.fullName}!`);
    }
  }
  </code></pre>
  
  <p>The error : </p>
  
  <pre><code>    [21:46:19] Plumber found unhandled error:
   SyntaxError in plugin 'gulp-babel'
  Message:
      D:/workspace/aurelia/navigation-app/src/app.js: Unexpected token (2:10)
    1 | export class Welcome {
  &gt; 2 |   heading = 'Welcome to the Aurelia Navigation App!';
      |           ^
    3 |   firstName = 'John';
    4 |   lastName = 'Doe';
    5 |
  [21:46:19] Finished 'build-system' after 20 ms
  </code></pre>
  
  <p>I have to say that I am on windows, it might create some troubles. </p>
  
  <hr>
  
  <p>I "solved" this problem by putting the variables in a constructor. But is the syntax above not valid ES6 ? is that ES7 or something not usable yet ? </p>
  
  <hr>
  
  <p>I know that this code looks weird but I am not the author, it is the original code from Aurelia tutorial</p>