version to 0.5.0
version to 0.5.0

* Update hard shutdown, raise shutdown error on threads (#17)
* Add custom error handling to workers (#18)
* Hotfix: Require the latest version of Assert (de88589)
* Consistent organization, cleanup comments, simplify timeout (#19)
* Add on worker error callback to `WorkerPoolSpy` (#20)
* Fix hard shutdown error always being raised by worker pool (#21)

/cc @kellyredding

redding/dat-worker-pool