Corrected the testing mock path.

It looks like the import path changed but the test wasn't updated. This
fixes the current test failure on Travis.
Requirements update.

Changed the requirements for redis and Flask to require a minimum version
and not an exact version. This is benificial if minor release is created
with a security fix. Previously we wouldn't have gotten that.

Added a minimum version for PyYAML.

Added nose to the dev requirements.