Abandons stderr special-casing:
* looks weird on shell and IO redirection to same file because of
interleaving of stdout and stderr
* better than a separate dedicated outlet because it does not require
additional configuration
fixes#28
BREAK SEMANTICS CONFIG
We lost the nice context-stack [jobname][taskname][...] at the beginning
of each log line when switching to logrus.
Define some field names that define these contexts.
Write a human-friendly formatter that presents these field names like
the solution we had before logrus.
Write some other formatters for logfmt and json output along the way.
Limit ourselves to stdout logging for now.
