Test on php 5.3.3 and set as the min version
Merge pull request #239 from GrahamCampbell/php533

PHP 5.3.3
Revert "Also test against hhvm-nightly"
Merge pull request #240 from thephpleague/revert-227-travis

Revert "Also test against hhvm-nightly"
Updated the upgrading guide
Merge pull request #242 from GrahamCampbell/upgrading

Updated The Upgrading Guide