message: Add missing git subtree informations.
diff: [date]
  path = src/elle/date
  url = https://github.com/HowardHinnant/date.git
  +[dopenssl]
  + path = src/elle/cryptography/modules/dopenssl
  + url = https://github.com/infinit/dopenssl
  +[drake]
  + path = drake
  + url = git@gitlab.gruntech.org:mefyl/drake
  