Fix bug in zadd where score and member was at the wrong position
Major commit with alot of changes.

 - Change default redis class from 'Redis' to 'StrictRedis' to fix some compability issues
 - Added support for RedisCluster as option as connection class.
 - Redisco have full support for RedisCluster. Uncomment code in __init__.py to enable it
 - Fixed all .lrem() calls after change to 'StrictRedis'
 - Fixed all .zadd() calls after change to 'StrictRedis'
 - Uncommented all Mutex code because of failing tests. If it can be made to work again then it will be uncommented again.