Created evolution file to add extra_data JSON field to

ChangeDescription model in order to pass in automate=True flag to 

track the originator of the close action when review request is closed 

by third-party repo services.

I have run ./manage.py evolve --execute to apply the changes to the 

database.
Even though unit test is not required to test for a newly added field, 

I did a quick sanity check if the extra_data field is added 

successfully to the ChangeDescription model. I have attached the 

screenshot to show that.