Uncaught reflect-metadata shim is required when using class decorators

[cmermingas]

• I'm submitting a ...
  [X] bug report
  [ ] feature request
  [ ] question about the decisions made in the repository
• Do you want to request a feature or report a bug?
  Report a problem
• What is the current behavior?
  I see error Uncaught reflect-metadata shim is required when using class decorators on the JavaScript console.
• If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem

One of my files is an AI player for a game and I want it to emit an event when it has decided its next move. So, I have this:

export class ConnectFourAiPlayerWebWorker {
  public nextMove = new EventEmitter<number>();

  constructor(public worker: Worker, public playerNumber: number) {
    worker.onmessage = (event: MessageEvent) => this.turnTaken(event);
  }

  takeTurn() {
    this.worker.postMessage('TAKE_TURN');
  }

  turnTaken(event: MessageEvent) {
    this.nextMove.emit(event.data);
  }
}

It was working until I added public nextMove = new EventEmitter<number>();. It then started giving this error in the browser's console: connect-four-ai-player-worker-wrapper.ts?21e7:3 Uncaught reflect-metadata shim is required when using class decorators

• Please tell us about your environment:
• Angular version: 2.0.0-rc.4
• Browser: Chrome 52.0.2743.116
• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. stackoverflow, gitter, etc)

I checked #353 but couldn't relate to the exact same problem. Plus, I don't think I would have to change the Webpack configuration or import new packages just to use EventEmitter. So my guess is that something else is wrong and chances are it's user error :-) Thanks in advance for your help!