Patch backup

I decided to store the backups generated with `bundle exec rake gitlab:backup:create RAILS_ENV=production` to a folder outside of the git repo.

This way, the git version determinationed needed for the metadata file backup_information.yml fails. The commit 067a8d5ff7bd736f996c81c245f5ce0936470669 solves this issue.

Beside this, the timestamp is given in binary. The problem is explained here: http://astrails.com/blog/2012/10/30/yaml-encodings-and-binary-strings

    :backup_created_at: !binary |-
      MjAxMy0wMy0xOSAxMzozMzozOSArMDEwMA==

The commit 7df78a9298667ee3333d834829bbdcf74d6706d3 solves this second issue.