Using PDO::CASE_NATURAL in default database connector

Though PSR1 doesn't force StudlyCaps, camelCase or under_score for property names using PDO::CASE_LOWER disables users from using StudlyCaps or camelCase for column names (properties in models). 



This should also be changed on: 
src/Illuminate/Database/Connectors/PostgresConnector.php 
src/Illuminate/Database/Connectors/SqlServerConnector.php

but since I don't use Postgre or MsSQL I decided to leave it to people with more expirience.