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)...
Track latest Credis_Client. Refs #50
Fix first run when LUA script does not yet exist. Refs #50
Fix log message.
Wrap CredisException with Zend_Cache_Exception in clean(). Track latest Credis_Client.
Track latest Credis_Client, use evalsha+eval rather than script exists+evalsha.