Removed Hiredis

It's been noted [before](https://github.com/mranney/node_redis/issues/483#issuecomment-23721272) on the node-redis issues lists that Hiredis shouldn't be used because the pure JS parser is faster than the native parser.

> But for the most part I suggest you don't use it, the current pure javascript parser is better supported in this library and faster for nearly all use cases.