Merge pull request redis#524 from go-redis/fix/nil-state

Don't panic if cluster state is nil.

Merge pull request redis#523 from go-redis/fix/timer

Fix wrong usage of timer Reset(), which could cause service frozen during master switch.

Merge pull request redis#512 from shogo82148/fix-wait-timeout

the timeout of WAIT command is in milliseconds.

Use simple PING for compatibility

Merge pull request redis#506 from go-redis/fix/separate-buffer

Separate read and write buffers for PubSub.

Merge pull request redis#486 from go-redis/fix/pubsub-receive

Fix ReceiveMessage to work without any subscriptions.

Merge pull request redis#481 from go-redis/fix/go18-tests

Fix error message for Go 1.8.

Merge pull request redis#474 from smacker/clone_and_context

Clone and WithContext redis#471

Merge pull request redis#475 from go-redis/fix/reduce-alloc

Reduce number of allocations.

Merge pull request redis#470 from go-redis/fix/remove-scanner

Remove Scanner in favor of ScanCmd.