simplify, clarify TextSentinel

codeclimate pointed this out. I agree it is better
to simplify and reveal intentions.
small refactor of RateLimiter for clarity
extract TopicNotifier class from topic
minor refactorings
Make pry a bit more useful
Sliding window rate limiting

Switched the algorithm to use a circular buffer
based on a redis list
Merge branch 'refactoring' of git://github.com/mattvanhorn/discourse

Conflicts:
	lib/text_sentinel.rb