Modify some examples
Added a small cache template for stress test so I don't piss of the OOM killer :)
Add an execv template for stress tests.
setting for optionally syncing on every scheduled task execution
More test case debugging
Make request.headers available for task.apply.  Closes #1874
Stress tests: adds logs and raising tasks
Task: callbacks and errbacks are now called as a group
Chords now calls callback.link_error
worker.heartbeat: Update 'interval' doc default to 2 seconds

Since the 30-second docs were written in 3eaffda (Hartbeat is now 30
seconds, but documented as 2 minutes, 2011-06-13), the default has
changed twice:

* It was reduced to 5 seconds by 387cf1c (Heartbeat frequency now
  every 5s, and frequency sent with event, 2012-03-28).
* It was reduced to 2 seconds by 6008303 (Persist clock value and
  synchronize revoked tasks with others, 2012-11-05).
Merge pull request #1879 from wking/worker-heartbeat-docs

worker.heartbeat: Update 'interval' doc default to 2 seconds
Adds amqp to list of packages
documentation, finer grained control on syncing, tests
Fixes typo
Gossip: Drop any task related events received by mistake (Issue #1882)
Redis docs now mention fanout_patterns caveat.  Closes #1882
Merge pull request #1876 from epantry/sync-scheduled-tasks

setting for optionally syncing on every scheduled task execution
Cosmetics for #1876
flakes
Merge branch 'ionelmc/extra-stress-template'