JIRA: https://jira.springsource.org/browse/INT-4343
* Add a `Executor` setter named `setTaskExecutor` in
`RedisInboundChannelAdapter` to set the container's task executor.
* Add a `task-executor` attribute to
`<int-redis:inbound-channel-adapter>`.
* Update RedisInboundChannelAdapterParser configuration validation
tests.
* Update redis.adoc and whats-new.adoc.
* Polishing according PR comments
* Improve `RedisQueueGatewayIntegrationTests` performance
a65de25572