Requirements: Remove factory_boy, allow SQLAlchemy 0.7.10

SQLAlchemy 0.7.10 is compatible with SQLAlchemy 0.7.x, so
allow it. Also remove dependency on factory_boy, which
seems to be unused.

Change-Id: Idb6bdf6ba02f2d826e2d11a9e2324f7d0a236a57
Merge "Requirements: Remove factory_boy, allow SQLAlchemy 0.7.10"