Go version >= 1.9

Cleanup some test code. Tests now require Go >= 1.9 (which is the earliest supported version)

ZADD INCR

Added support for the 'INCR' flag to the 'ZADD' command.

Lua cjson

Lua changes:

• added cjson library
• added redis.sha1hex method

Lua

Added support for Lua (EVAL', EVALSHA, and SCRIPT`).