hubot: Add jenrzzz/hubot-logger

This logger is not in the node index (which points to
adragomir/hubot-logger [1,2]).  However, Jenner's package has more
recent activity (one month ago, vs. five for Andrei), and seems more
featureful.  I also approve of using Redis (instead of on-disk files)
for log storage.

[1]: https://www.npmjs.org/package/hubot-logger
[2]: https://github.com/adragomir/hubot-logger