add queue check before pull/process/push

[jgpawletko]

Current implementation does a "pull/process/push" even if there are no requests in the queue.
Add a method, e.g., Processor#any_work? that returns false if the request queue is empty, and
returns true if there are queue entries.

This will enable one to tweak the rake file so that the pull, process, push tasks are only executed if Processor#any_work? is true.

This will eliminate unnecessary GitHub interaction.