Added support of Predis library as storage adapter
Since predis library is a well-known alternative to phpredis, I've decided to add an extension to Redis storage adapter.
Some properties and methods were changed to protected in order to handle slight differences between these 2 libs.
Mostly additional params are passed as an array in phpredis and as single arguments in predis.
I'm currently looking into adding RedisCluster support (see #153). Probably we could join forces by rewriting the Redis adapter and include the if/else for handling Predis transparently and hiding the complexity to any user (DX++). WDYT?
Is there any update on this? I'd love to get support for Predis in here so that I can use some additional stuff in production.