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.

Enjoy.

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*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>