Removed configuration for default runner from hub.

Refactored `publish` to be responsible for adding the `:hub_pipeline` to the event.

Update tests.
Copy relevant code for `subscribe` vs. calling emit.
Fix indentation.
We can `continue` instead of `break` with label.
Removed the config module for hub which is not featured any more.
Merge pull request #139 from troopjs/feature/hub-publish-subscribe-explicit

Make explicit runners only available for emit