Add afterRender event in toolbar

So that you don't have to call 

```php
echo $toolbar->render();
```

now the call can be 

```php

$di->set('profiler',
    function () {
        return new \Fabfuel\Prophiler\Profiler();
    },
    true
);

$di->set('toolbar',
    function () use ($di) {
        $profiler = $di->get('profiler');
        $toolbar = new \Fabfuel\Prophiler\Toolbar($profiler);
        $toolbar->setEventsManager($di->get('eventsManager'));
        return $toolbar;
    },
    true
);

$toolbar = $di->get('toolbar');
```