addUserToGame(gameUid: string, user: firebase.User): Observable<void> {
  return Observable.fromPromise(
    this.db.object(`joinedUsers/${gameUid}/`).update({[user.uid]: {username: user.displayName, count: 0}})
  )
  .take(1)

addUserToGame(gameUid: string, user: firebase.User): Promise<any> {
  return this.db.object(`joinedUsers/${gameUid}/`)
    .update({
      [user.uid]: {username: user.displayName, count: 0}
    });
}

addUserToGame(gameUid: string, user: firebase.User): Observable<void> {
return Observable.fromPromise(
  this.db.object(`joinedUsers/${gameUid}/`)
    .update({
      [user.uid]: {username: user.displayName, count: 0}
    }).take(1)

addUserToGame(gameUid: string, user: firebase.User): Observable<void> {
  return Observable.fromPromise(
    this.db.object(`joinedUsers/${gameUid}/`)
      .update({
        [user.uid]: {username: user.displayName, count: 0}
      })
      .take(1)

addUserToGame(gameUid: string, user: firebase.User): Observable<void> {
  return Observable.fromPromise(
    this.db.object(`joinedUsers/${gameUid}/`)
      .update({
        [user.uid]: {username: user.displayName, count: 0}
      })
    )                 // NEED RIGHT PAREN TO CLOSE CALL TO FROMPROMISE
    .take(1);
}

Observable.fromPromise(promise).take(1).subscribe(x => console.log(x))

Observable.fromPromise(promise).subscribe(x => console.log(x))

promise.then(x => console.log(x))