Updated the workflow_creation.py according to the recommendations made by Serge
Updated the workflow_creation.py according to the recommendations made by Serge

1) Slightly modified the comments to tell that we are creating a separate file called as my_workflow.py in <dipy/workflows> folder.
2) Removed the first line about the import statements.
3) Comments are more precise now.

FrancoisRheaultUS/dipy,FrancoisRheaultUS/dipy