redis, timeout and pipeline changed to non-static
Callback separated out as as a callable class.
SS-2029
1. Added evalsha, script_exists, script_flush, script_load to emulate redis.Redis (from redis-py).
2. Additional script_exists_single, register_sha.
TODO: script_kill (Will probably create a separate story to address this)
- added test cases for scripting functions
- added lua script to initialize KEYS and ARGV arrays
- added constants for test string literals
SS-2029