Ability to add multiple users to the GTalk notification service

Made some small modifications so you can specify more than one user (`room_id`) to the Gtalk notification service.

Now you can add more than one user by separating them by `,` `;` or just a space.

examples:
```
user@domain.com, another_user@domain.com
user@domain.com; another_user@domain.com
user@domain.com another_user@domain.com
```