Changes

use cp; rm instead of mv to transfer the tito output to _output.
When running 'make release' as root with the source mounted in via NFS
and root_squash set (e.g., when using Vagrant), mv will move normal
files correctly
(but complaining about not being able to set the uid/gid), but it will
fail to move symlinks (same complaint, then exit(1)).
Unhappily for us, _output contains a symlink, hence this workaround.
 (commit: 23661a9)

bump(github.com/boltdb/bolt): v1.3.0
 (commit: 71d6fd5)