Install VBoxGuestAdditions in vagrant box

install_vb_additions.sh

function install_vb_additions
{
    local VB_VERSION="$1";
    local download_url=http://download.virtualbox.org/virtualbox/${VB_VERSION}/VBoxGuestAdditions_${VB_VERSION}.iso
    curl -C - -O $download_url
    sudo mkdir /mnt/iso
    sudo mount -o loop VBoxGuestAdditions_${VB_VERSION}.iso /mnt/iso
    sudo yum install -y kernel-devel-`uname -r` gcc make perl bzip2
    pushd /mnt/iso
    sudo ./VBoxLinuxAdditions.run
    popd
    sudo umount /mnt/iso
}