Merge pull request colinmollenhour#102 from Xon/latest_credis

Track latest Credis

Fix unit tests. Track latest Credis.

Add chunking to use_lua mode as well. Minor optimization without lua …

…mode (do not array_unique if not needed).

Track latest Credis library (adds auto-retry on first request failure).

Fix unit tests randomly failing.

Track latest Credis_Client, use evalsha+eval rather than script exist…

…s+evalsha.

Allow keys to be set without expire times. Refs colinmollenhour#33

Prevent cache tag data from being lost in race conditions. Refs colin…

…mollenhour#33

Tracking latest lib/Credis (minor)

Always select db in case connection is used elsewhere.