:envvar:`C_STRICT_APP` now outputs traceback to stderr if something falls back to current_app
Canvas should not use current_app, instead take the app from the first task.  Closes #1249
fixes chord/chain
tests passing
Remove some itertools/operator usage
Adds sep argument to functions in .utils.text
map -> listcomp
Merge branch '3.0'

Conflicts:
	celery/__init__.py
	celery/app/annotations.py
	celery/app/builtins.py
	celery/app/utils.py
	celery/apps/worker.py
	celery/backends/base.py
	celery/bin/base.py
	celery/bin/celery.py
	celery/bin/multi.py
	celery/canvas.py
	celery/contrib/rdb.py
	celery/loaders/base.py
	celery/result.py
	celery/task/http.py
	celery/utils/__init__.py
	celery/utils/log.py
	celery/utils/mail.py
	celery/utils/text.py
	celery/utils/timer2.py
	celery/worker/control.py
	celery/worker/hub.py