fix(client): re-parse docopt
fix(tests): use streamOutput for test runs
Merge pull request #2219 from gabrtv/test-buffering

fix(tests): use streamOutput for test runs
fix(builder): work around 0-byte ADD layer by ignoring tar timestamps
Merge pull request #2222 from gabrtv/fix-builder-add

fix(builder): work around 0-byte ADD layer by ignoring tar timestamps
Merge pull request #2216 from bacongobbler/fix-releases-list

fix(client): re-parse docopt
ref(builder): compress archive into tarball

When we removed pigz from slugbuilder, it changed the format to a
tar file. Compressing it with gzip by supplying tar the -z option
reverts this behaviour.