Update redis version to fix issue using redis namespaces

When a namespace is specified in the initializer, enqueuing jobs encounters an error:

```
2013-08-20T14:55:16Z 34503 TID-ox3zgd90c INFO: Sidekiq client using redis://localhost:6379/0 with options {:namespace=>"postal_service"}
NoMethodError: undefined method `is_a?' for <Redis::Future [:sadd, "postal_service:queues", :postback]>:Redis::Future
```
[ [full stack trace](http://gist.io/6284596) ]