Async jobs don't run when added to a task obtained via find

[toddthomas]

It's common to obtain a reference to an already created task using the find class method.

task = Resque::Plugins::MultiStepTask.find(task_id)

If you then try to add a job to that task

task.add_job(SomeJob)

the job is never queued: that only happens if the task is started, which is tracked by an instance variable that isn't persisted.

[toddthomas]

See example added to branch issue-4.

[DCameronMauch]

This bug has been identified, and I believe fixed. Add another test along with yours, which are both now passing. We will be doing some manual testing just to verify.