Change uses of Job.queue to Job.enqueue.
Merge branch 'master' into 0.6-docs
Update docs for priority and run_at variable renamings.
Fix a strangely worded changelog entry.
Add docs on multiple queues.
Merge branch 'master' into 0.6-docs
Document Que.enqueue.
Add a doc on schema migrations.
Merge branch 'master' into 0.6-docs

Conflicts:
	CHANGELOG.md
Add changelog entry on migrating the schema when upgrading.
Fix changelog typo.
Merge branch 'master' into 0.6-docs

Conflicts:
	CHANGELOG.md
Minor documentation tweaks.
Add docs on shutting down safely and using timeouts in jobs.
Add documentation on running with Puma (and presumably Unicorn).
Bump version to 0.6.0.