Update redis module version

We are experiencing some issues with redis 0.8.2, that are fixed in 0.8.3 and 0.8.4. Specifically "Fix SMEMBERS order dependency in test broken by Redis changes (Garrett Johnson)" (see changelog https://github.com/mranney/node_redis/blob/master/changelog.md).

Using "redis": "0.8.4" fixes the issues.