Thread of execution depends on event's listeners.

If we have a few of subscribers and one of those throws an exception, our thread of execution well be interrupted.

For example:

```
var hub = new Mediator();
hub.on('test', function func1() { console.log(1); });
hub.on('test', function func2() { throw new Error('test error'); });
hub.on('test', function func3() { console.log(3); });

hub.trigger('test');
console.log(4);
```

Actual result:

```
1
throwing exception
```

Expected result:

```
1
3
4
and throwing exception with stacktrace
```