Add ability to use AS statement in queries

This will add the ability to do an AS statement in your queries and not break the result
e.g. 

$result = DB::table(str_plural($this->model))->where('account_id', '=', 333)->select('id', 'title', DB::raw("LEFT(contents, 40) AS contents"));
return Datatables::of($result)->make();
Merge pull request #33 from Clooner/patch-1

Add ability to use AS statement in queries