Correct iso8601 parseing invalid year num

iso8601 should raise reasonable error when parsing timestamp with invalid
years. This is implemented in iso8601 version 0.1.9.
More details please see the bug description and the issue on bitbucket.

Change-Id: I23ec6a125110294f49eb55ced02ff4e5965a0b99
Closes-Bug: #1266398
Revert "Switch to SQLAlchemy 0.9"

This reverts commit fde324efaf57decd1a33dc61bb1f5f9e93f4d79b
Merge "Revert "Switch to SQLAlchemy 0.9""
Merge "Correct iso8601 parseing invalid year num"
Rename Savanna to Sahara

Change-Id: Ied6f746c286ece66a0f0fa91a08459032c72f20e