Make it possible to continue the chain of jobs when one of the jobs failed (or when a worker failed when run on all workers is selected).
Add method (mark_failed) to manually mark a run as failed.
Add test to test mark_failed on completed run.
Make publisher a variable of the Command class.
Add _mark_worker_runs_as_failed to mark runs for a given worker as failed.
Close the event_publisher.
Add _find_unresponsive_workers_and_mark_runs_as_failed.
Move save to the end (when log has been created).
Wire up _find_unresponsive_workers_and_mark_runs_as_failed.
Update README.
Add missing docstring. Fix typo.
Fix typo.
Move worker ping-response check to health_check management-command.
Cleanup.
Add is_responsive method to Worker model.
Add e-mail notification when all workers in a pool are unresponsive.
Update docs.
Update README.
Merge remote-tracking branch 'spilgames/master' into run_on_all_continue_on_error

Conflicts:
	README.rst
	job_runner/__init__.py
Typo fix.