Fix Vagrant VM link in README
Fix Vagrant VM link in README

akgood/yubico-piv-tool,akgood/yubico-piv-tool,Yubico/yubico-piv-tool,akgood/yubico-piv-tool,Yubico/yubico-piv-tool,Yubico/yubico-piv-tool,akgood/yubico-piv-tool