expose the current scheduler key
added RACTargetedQueueScheduler
Revert "expose the current scheduler key"

This reverts commit 7c20a1c1449ad960496af328d50dcf00df418417.
support RACQueueScheduler subclasses
derp
use the proper import style
actually do the schedule
don't import subclass in the umbrella header
fix the import style
move queue to the private category
clarify docs
don't overretain self
volatile
more docs
test some things
fix races with the current scheduler
expose RACTargetedQueueScheduler
fix import style
—volatile
rename RACTargetedQueueScheduler