Add maximum responses version.
Add maximum responses version.

Version 0.10.3 of the responses module introduced a regression that breaks several unit tests.

gregbdunn/aws-ec2rescue-linux,Drudenhaus/aws-ec2rescue-linux,gregbdunn/aws-ec2rescue-linux,Drudenhaus/aws-ec2rescue-linux,gregbdunn/aws-ec2rescue-linux,Drudenhaus/aws-ec2rescue-linux