Implement enqueue_at/enqueue_in

Delayed jobs are supported by all systems except QueueClassic.  For it I decided to raise NotImplementedError.

The inline implementation is a bit rough.
remove debugging
merge master
Move past time check out of adapters
Add logging for enqueued_at and perform errors
Fix boogs, stub not implemented adapters
Assert truthy
merge master
More feedback
cleanup
Switch to NIE
Remove unnecessary comment
mergy
Merge pull request #35 from mperham/enqueue_at

Implement enqueue_at/enqueue_in