Add an interface for keyed operation queue

This will allow us to remove the implementation we have in GHfW and use
this one instead.
Make method static

Doesn't need to be an instance.
Simplify conditional

This is an automated refactoring.
Removed unused code
Remove outdated stress test

We have the new Stresser class for creating stress tests.
Add ShutdownQueue to interface
Merge pull request #36 from github/add-koq-interface

Add koq interface