Make Redis Ack Emulation More Consistent with AMQP

Currently when the Redis transport restores unacknowledged messages they are put on the back of the queue `lpush` rather than the front `rpush`. This is inconsistent with how unacknowledged messages are restored when using RabbitMQ/AMQP. I created a gist example to demonstrate this difference: https://gist.github.com/mlavin/6671079