Update CHANGELOG.md for 1.3.0 release
Update CHANGELOG.md for 1.3.0 release

aws/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent,aws/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent,swipely/amazon-ecs-agent,swipely/amazon-ecs-agent,swipely/amazon-ecs-agent,swipely/amazon-ecs-agent,aws/amazon-ecs-agent,aws/amazon-ecs-agent,jaimeguzman/amazon-ecs-agent,jaimeguzman/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent