Packer/http/ks.cfg: Added kernel, kernel-devel, and kernel-headers as required packages. This ensures that the guest additions can be built.
Packer/http/ks.cfg: Added dependency yum-plugin-versionlock and added kernel, kernel-devel, kernel-headers versions to the yum locked list. This way they will not be inadvertently updated when yum updates everything.
Packer/http/ks.cfg: Added other kernel components to the packages list and froze their versions as well. This way if they are required by other packages, they are already installed and are the same version as the kernel, which they will remain.
Vagrant/Vagrantfile: Added the url to the box file in the GitHub repo.