Adding the ability for configurable blade content tags.

This PR, in relation to [laravel/laravel #1759](https://github.com/laravel/laravel/pull/1759) adds the ability to change the tags used in Blade when echoing. You know, the ``{{ $val }}` tags.

Additionally, the raw content tags, `{{{ $raw }}}` have also been setup to be configurable as well as the comment tags.

Within the scope of Laravel, it's as easy as changing  your `app/config/view.php` file to suit. Outside, you simply call `setContentTags(array('[[, ']]'); // Whatever you want``.

It now becomes easy to change your views to be like so (if you want):

```html
@section('content')

[[ $firstName ]]

@stop
```

Enjoy.

---

*In Taylor's last talk at Laracon, somebody mentioned something about Blade compilers conflicting with other libraries. I've also experienced this problem and in true PR or STFU, I've done exactly that.*

Signed-off-by: Ben Corlett <bencorlett@me.com>