deploy:dogestry:pull_image is now a 2 steps process.

1. Centurion will tell dogestry to download image from S3 in single thread. Don't worry, dogestry itself downloads in multi-thread fashion.

2. Centurion will then tell dogestry to generate and upload TAR file in multi-thread.

Don't worry about the number of commits, those are side effect of `git merge upstream/master`, just look at number of files changed.
Since we don't do anything with these except pass them to `Dogestry.new` I would prefer to just pass them in the call rather than storing them in a hash first.