* Documentation! The README is obviously not enought to show how to use 
  Predis as it does not cover all of its features.

* The included test suite covers almost all the Redis server commands, but a 
  full battery of tests targeting specific functions of this library is still 
  missing.

* Missing tests for new commands: 
    ZSets   : ZREVRANK, ZREMBYRANK, ZUNION, ZINTER
    Hashes  : HSET, HGET
