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

closes #1400

I also formatted the logger module correctly with `go fmt`.
So is "tag" what the first word of the message is classified as?