Sendfile, #10, prevent php files from being downloaded

- Fix second vagrant up that fails (by restricting to PHP 5.3 - added this as a hotfix for #10)
- Prevents php files from being downloaded in nginx
- Added `sendfile off;` in nginx config. This is an issue with vagrant shared folders which ends up serving corrupted files (in my case it was serving corrupted js/css files) - http://docs-v1.vagrantup.com/v1/docs/config/vm/share_folder.html