fix(logger): add back message tag

without the tag, the first word from the logs was missing.

Without this change:

    2014-07-23 16:29:05 oblong-duckling[worker.1]:  world

with this change:

    2014-07-23 16:38:19 oblong-duckling[worker.1]: hello world
Merge pull request #1402 from deis/fix-logger-output

fix(logger): add back message tag