Refactor for test-, mock-ability
Add ability to publish measurements via Redis pub/sub

When REDIS_PUBLISH is set to something other than `no`, publish
measurement with Redis PUBLISH command.  This allows other tools to
consume the measurements in real time.
Add comments
Update test data for correctness

This is closer to what's actually sent by sensord
Update README, make REDIS_PUBLISH flag consistent

REDIS_PUBLISH and LOGSTDERR are both boolean flags; they should be
enabled the same way.
Merge pull request #59 from blalor/publish_measurements

Add ability to publish measurements via Redis pub/sub