SQLAlchemy requirements put in order

- require SQLAlchemy>=0.7.8 if no stricter requirement present;
- allow SQLAlhchemy 0.9.x in python 3.3 and pypy test environments.

Change-Id: I8ee29c66612e8051a26a1633c0973d0dfa048fc4
Merge "SQLAlchemy requirements put in order"