Adding a check to make sure people are not using too old version of vagr...

...ant.

They wouldn't be able to use the vagrant cloud functionnality.
My suggestion:

If your Vagrant version is lower than 1.5, you can still use this provisioning by commenting the line below and providing the config.vm.box_url parameter, if it's not already defined in this Vagrantfile. Keep in mind that you won't be able to use the Vagrant Cloud and other newer Vagrant features. It's strongly recommended that you update your version as soon as you can. Check the official downloads page to get the newest Vagrant: https://www.vagrantup.com/downloads.html