Merge tag 'sparks-2.5.2' into develop

2.5.2
Update the templates to use 2 new context variables, and customize one of them when there is more than one worker on the same machine, as advised at http://docs.celeryproject.org/en/latest/userguide/workers.html#starting-the-worker.
Update description & keywords.
bump version in setup.py
Merge branch 'release/2.6'