Feature/inclusive exclusive range sorted sets

- Added optional params to SortedSet score method
- Used new params in implementation of zrevrangebyscore, zremrangebyscore, zrangebyscore  as per http://redis.io/commands/zrangebyscore (see Exclusive intervals and infinity)
- Added tests to cover new code

tried work with git flow this time... I hope I did it correctly... please let me know if I missed something.