Tweaks for oracle.
Revert to PickleType.
Fixes confusing argument errors for task decorator.  Closes #1692
Merge branch 'trevorskaggs/oracle-tweaks'
Django: Perform model validation on worker init.  Closes #1681
Import StringIO/BytesIO from io module
Fixed incorrect eta when countdown is used with timezone setting.
Canvas: Unroll groups with only one item.  Closes #1656
Fixes django tests
Forgot to push change for Issue #1656
Merge branch 'anti-social/fix_countdown'
Tests passing
Memcache keys are unicode on Py3.  Closes #1697
Update trace.py

Looks like #1684 also ;)
Beat attempts to drop privileges twice with --detach.  Closes #1708
Small asynpool fixes
Task name can be None #1710
set script name correctly when invoked via sysv-style init
Update outdated control command example.  Closes #1680
Now depends on billiard 3.3.09