optionally use lua scripting for cache cleaning (_removeByMatchingAnyTags method) configurable by the new "use_lua" backend setting (turned off by default).
CAUTION: requires commit 1c101cf5543624 to CRedis submodule in order to work properly.
Merge pull request #50 from nemphys/lua-clean

optionally use lua scripting for cache cleaning (_removeByMatchingAnyTags method)...