Added FlashMessenger View Helper

Hi

I have added support for flashMessenger, it creates alert boxes according to messages status, eg. in controller
```php
$this->flashMessenger()->addInfoMessage('This is a info alert');
```
will create:
```html
<div class="alert alert-info">
    <button type="button" class="close" data-dismiss="alert">&times;</button>
    This is a info alert
</div>
```