Add Predis connection component

Hi Charles,

   I happen to use predis (instead of phpredis) because of several restrictions and limitations on my project's production servers. I found your components pretty useful but the only chance I can take advantage of them is to get a PredisConnection component similar to your RedisConnection component.

   I'm committing a APredisConnection component I've written and used in my project successfully in conjunction with your ARedisCache. Feel free to modify it so it fits your coding standards.