Add optimization for '*' pattern in PubSubChannels.
Merge pull request #47 from go-redis/fix/pub-sub-empty-pattern

Add optimization for '*' pattern in PubSubChannels.
Fix PubSubNumSub to work with Redis 2.8.14.
Merge pull request #50 from go-redis/fix/upgrade-to-redis-2814

Fix PubSubNumSub to work with Redis 2.8.14.
sentinel: don't leak goroutines on sentinel fail. Fixes #48.