Spring Data Redis 1.4.0 introduced Redis Sentinel support. When
specified, RedisConnectionFactory uses the Sentinel configuration to
determine the current master.

Sentinel configuration can be specified using two new properties:
spring.redis.sentinel.master and spring.redis.sentinel.nodes.

For example:

spring.redis.sentinel.master=mymaster # name of redis server
spring.redis.sentinel.nodes=127.0.0.1:26379,127.0.0.1:26380

Alternatively, a bean of type RedisSentinelConfiguration can be declared
and it will be used to configure the connection factory.

Note: At this time, Sentinel support is only available for Jedis

Closes gh-1337