Added some easy access method

Works done:
-Added dependency on Illuminate\Support package (Laravel 4)
-Created PHPUnit configuration file (phpunit-composer.xml) to test using
the composer autoloader
-Implemented Illuminate\Support\Contracts\ArrayableInterface (Laravel 4)
on PropertyContainer and ResultSet
-Implemented Illuminate\Support\Contracts\JsonableInterface (Laravel 4)
on PropertyContainer and ResultSet
-Changes on the SearchIndex::handleResult to return ResultSet instead of
array