Don't monkeypatch when Open Dispatch Club suffices
Merge instead of or default config

- Allows users to only specify options they want to override
Breadth-first instead of depth-first dispatch

- Minimizes number of times fixtures need to be invoked
- Should lead to nses getting walked in tighter loops with less thread
  coordination overhead
- Initial performance testing suggests more wall clock speedup than
  depth-first strategy
Release 0.3.0