Pin SQLAlchemy to 0.7.x

0.7.10 has been released and is compatible with 0.7.x. Instead
of pinning to 0.7.9, simply pin to 0.7.x to avoid SQLAlchemy 0.8

Change-Id: Iea57598698b4faf906e82a2974497221d07f4d16
Merge "Pin SQLAlchemy to 0.7.x"