Multiserver

Hi Colin,

I noticed that Cm_Cache_Backend_Redis can only connect to a single Redis server. For larger setups, it would be nice if we could leverage the Credis_Cluster features.

This pull requests offers Credis_Cluster support with backwards compatibility for the current configuration syntax.

Could you please review the pull request and give me feedback? Could you also explain how I can actually test this on a recent Magento installation where Cm_Cache_Backend_Redis is already there by default?

Cheers
Thijs