Version 0.5.1

• Exported shares are now resolved relatively to the directory of the
  main cluster description file, which helps migrating project trees
  if necessary.
• Mounted shares (still VirtualBox only) will persist reboots of the
  virtual machines through adding a specific section to
  /var/lib/boot2docker/bootlocal.sh or creating the file if necessary.
• Shares can now have a type which defaults properly to vboxsf on the
  virtualbox driver and to (new type) rsync on all other drivers.
  This will use rsync to copy the content of a host directory at VM
  creation and to copy back the content of the VM directory using the
  new sub-command called sync. Running machinery sync as a cron
  job is then probably a good solution.
• Fixed bug that would prevent machinery to mount some of the shares
  using vboxsf.
• Adding support for human-readable sizes, e.g. 10G for 10 gigabytes
  (powers of 1000), or 1GiB for 1 gigibytes (powers of 1024
  instead!).
• Adding support for user-specified ssh command, which will be used
  in place of the one that is guessed from introspection of
  docker-machine ssh whenever possible.
• Using the new docker-machine scp sub-command for file copy
  operations when it exists.
• Added possibility to recreate the shares and mount them from within
  a reinit call. This isn't entirely tested yet and will fail
  reusing shares if they had already been created in the past.
• Added possibility to read program options from configuration file
  through -config global option (handy when specifying complex ssh
  commands for example).
• Added ps command to return the status of the whole cluster (via
  the swarm master).
• ssh sub-command now can be called without arguments to get a
  prompt into virtual machine (thus being a (handy?) relay to
  docker-machine ssh).