1.0.20160829211335

Revert isinstance(step_entry, (str, unicode)) because typing.Text is …

1.0.20160829192223: Packing refactor (#177)

* Refactor 'pack into single graph' functionality into separate module.
* Don't modify input step object in WorkflowStep, copy it instead.
* Use Text type
* Add test for packing feature.
* Sort output pack output for deterministic results.