print version when removing a specific box

Example:

$ vagrant box remove --box-version 0.2.9 berendt/ubuntu-14.04-amd64
Removing box 'berendt/ubuntu-14.04-amd64' with provider 'virtualbox' in version '0.2.9'...
Merge pull request #3438 from berendt/show_version_when_removing_a_specific_box

print version when removing a specific box