Use timer to more accurately set retry delay times.
Add more logging output, isolated kwargs manipulations
Moved away from invoking retry task on queue due to direct callback issue.
Add busy logic to scheduler method in case tasks take too long
Add debug indicating if the scheduler was busy or not
Cleanup and added docs
Centralized logic for when a task should be retried or not.
Add logging to troubleshoot pending verification issue
Mods to better understand error messages
Restore back invoking retry tasks remotely on queue.
Removed ponderous debug output.
Remove redundant scheduling parameter.
Add clarifying language about immediate task retry callback; Fixed inaccurate unit test;
Add documentation to explain how the queueing package works.
Merge pull request #734 from jfwood/verify-resource

Improve retry task timeout logic and interaction with invoked tasks.