Upgrade from 2.8.19 to 3.0.0.
Merge all changes from databases/redis-devel to databases/redis.
Redis 3.0 release notes
--[ Redis 3.0.0 ] Release date: 1 Apr 2015
>> What's new in Redis 3.0 compared to Redis 2.8?
* Redis Cluster: a distributed implementation of a subset of Redis.
* New "embedded string" object encoding resulting in less cache
misses. Big speed gain under certain work loads.
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