Steps cannot find dependencies if listed downstream in json

[wukevin]

Within the zippy json file, if a step has a dependency that is listed further down in the json file than it itself is, it cannot successfully find that dependency. While this is easily worked around (by simply rearranging the json) it could possibly become cumbersome for more complex pipelines.

Example error message that this triggers:

[ERROR] Failed to complete master workflow, error code: 1
[ERROR] errorMessage:
[ERROR] Unhandled Exception in TaskRunner-Thread-masterWorkflow
[ERROR] Traceback (most recent call last):
[ERROR]   File "~/software/python/lib/python2.7/site-packages/pyflow/pyflow.py", line 1069, in run [ERROR]     (retval, retmsg) = self._run()
[ERROR]   File "~/software/python/lib/python2.7/site-packages/pyflow/pyflow.py", line 1121, in _run
[ERROR]     self.workflow.workflow()
[ERROR]   File "~/software/python/lib/python2.7/site-packages/zippy/zippy.py", line 164, in workflow
[ERROR]     previous_stages = [self.stage_dict[x] for x in stage.previous_stage]
[ERROR]   KeyError: u'example'