Show object when throwing "non-persisted record" error

When calling `delay` on a non-persisted record, the error raised now also contains the details about the object.

This make debugging this error easier. And is consistent with the previous error.
fix specs non-persisted records error
Merge branch 'master' of https://github.com/collectiveidea/delayed_job into patch-1

Conflicts:
	lib/delayed/backend/shared_spec.rb
	lib/delayed/performable_method.rb
Merge pull request #655 from Dorian/patch-1

Show object when throwing "non-persisted record" error