Add Closeable to JedisPool.

This allows JedisPool instances to also participate in try-with-resources.

Adds tests (both for JedisPool and the Jedis code itself).
Merge branch 'closeable' of https://github.com/hgschmie/jedis into pool-closeable-support
Add "closeable" unit tests to JedisSentinelPool, ShardedJedisPoolTest
Replace Closer class to use its close() method
Merge branch 'pool-closeable-support' of https://github.com/HeartSaVioR/jedis into HeartSaVioR-pool-closeable-support