Atomic version of Resque.schedule=
Atomic version of Resque.schedule=

This pipelines the clear_schedule and set_schedule to
remove conflict with other processes simultaneously
calling schedule=

See #437

resque/resque-scheduler,carsonreinke/resque-scheduler,adaptiv-io/resque-scheduler,adaptiv-io/resque-scheduler,carsonreinke/resque-scheduler,playtestcloud/resque-scheduler,xldenis/resque-scheduler,carsonreinke/resque-scheduler,guizmaii/resque-scheduler,stvp/resque-scheduler,mfo/resque-scheduler,playtestcloud/resque-scheduler,guizmaii/resque-scheduler,playtestcloud/resque-scheduler,StitchedCode/resque-scheduler,kangkot/resque-scheduler,adaptiv-io/resque-scheduler,StitchedCode/resque-scheduler,mfo/resque-scheduler,resque/resque-scheduler,StitchedCode/resque-scheduler,stvp/resque-scheduler,xldenis/resque-scheduler,resque/resque-scheduler,mfo/resque-scheduler,stvp/resque-scheduler,xldenis/resque-scheduler,kangkot/resque-scheduler,guizmaii/resque-scheduler,kangkot/resque-scheduler