updates requirements.txt for django-bakery==0.2.2

This allows the user to specify an s3cmd file allowing table-stacker to bake to different s3 buckets.  Incidentally, I noticed that django bakery is at v0.3.0 now.  I tried changing the requirements file to that version of django-bakery but v0.3.0 breaks buildserver.  I'll file a separate issue.