Bump PHP 5.3 version due to openssl issue

See travis-ci/travis-ci#1385. There are issues with SSL extensions not
fully working in PHP 5.3.3, causing `composer install` to fail.

I've added a check to the functional tests to make sure that the PHP server is running. I considered a simple version check but I thought it might be possible that the server and the code under test could be ran with different PHP versions (e.g. always run the test server on PHP 5.4+ even if the code is being tested on 5.3. I played around with `phpenv` a little but had no luck).

Additionally, I've added the CURLFile changes for PHP 5.5 support, as in #136.