Move required PHP version to 5.3.3

There does not appear to be a reason this is set to PHP 5.3.10

Moving to PHP 5.3.3 aligns with the default version in CentOS and falls
under other distributions. Ubuntu 12.04 LTS does provide 5.3.10.
Merge pull request #3 from mkly/move_required_php_version_to_5_3_3

Move required PHP version to 5.3.3