Merge pull request #45 from andrewhoff/master

Handle both redis response codes on PTTL

drivers/store/redis/store.go

@@ -230,8 +230,11 @@ func updateValue(rtx *libredis.Tx, key string, expiration time.Duration) (int64,
 		return 0, 0, err
 	}
 
-	// If ttl is negative, we have to define key expiration.
-	if ttl < 0 {
+	// If ttl is -1, we have to define key expiration.
+	// PTTL return values changed as of Redis 2.8
+	// Now the command returns -2 if the key does not exist, and -1 if the key exists, but there is no expiry set
+	// We shouldn't try to set an expiry on a key that doesn't exist
+	if ttl == -1 {
 		expire := rtx.Expire(key, expiration)
 
 		ok, err := expire.Result()