Add support for dynamically changing the schedule (match functionality of Resque 2.x)

[cballou]

From the Resque README, they now support dynamically changing the schedule:

# If you want to be able to dynamically change the schedule,
# uncomment this line.  A dynamic schedule can be updated via the
# Resque::Scheduler.set_schedule (and remove_schedule) methods.
# When dynamic is set to true, the scheduler process looks for
# schedule changes and applies them on the fly.
# Note: This feature is only available in >=2.0.0.
#Resque::Scheduler.dynamic = true

https://github.com/bvandenbos/resque-scheduler