pipeline: Uses a set for requisite_urls. Uses remove() to reduce memory leak.
Bumps pipeline version 20140411.01
Add /jetpack-comment/ ignore pattern
Ignore &replytocom= as well
Dashboard: ignore Sass cache.
IA pack finder: switch to archivebot collection.
Publish a message when job settings change.

At present, a pipeline checks its settings after every request; however,
settings change relatively infrequently.  This polling behavior is
therefore unnecessarily heavy, and (I suspect) is slowing down pipeline
execution.

The Right Thing to do is to have each pipeline listen for change
notifications and update their job data when such a notification is
received.  (Pipelines should still poll -- it ensures that a pipeline's
job settings are in sync, and provides a way to recover from control
node communication failure -- however, we can poll at a much reduced
rate whilst minimizing blockage on the main thread.)
Switch to bleeding-edge redis-py.

Andy McCurdy has merged a large number of changes to redis-py's pubsub
implementation.  Of particular interest is pubsub.run_in_thread(), which
subscribes to a pubsub channel on a separate thread.  In released
versions of redis-py, doing this is very painful.

These changes are scheduled for redis-py 2.10.0, which is not yet
released.  Hence this commit.
Use per-job pubsub channel.
Add missing colon.
Disambiguate string in shared config.
Topic branch-enabled non-descript change stashing.
Remove unused wpull.control.Control.
I promise to tease this apart into coherent commits.
A webapp for ArchiveBot integration testing.