Use io.BytesIO instead of sqlalchemy.byte_buffer

application_package uses byte_buffer to write an in-memory
zipfile. byte_buffer wasn't introduced into sqlalchemy until
v0.9 as part of the python3k compat changes. Patch changes
application_package to use io.BytesIO instead.

Alternative is to change the sqlalchemy and -migrate package
versions.

Change-Id: I59f23d2ed4e37063dca4d2a70e9f6184bd0e0aeb
Closes-Bug: 1309743
Merge "Use io.BytesIO instead of sqlalchemy.byte_buffer"