adding support for JedisSentinelPool

Added support for JedisSentinelPool which is in the jedis master branch. The official 2.2.2 release doesn't seem to be available yet but someone manually packaged it up and uploaded it to maven central (http://search.maven.org/#artifactdetails%7Cnet.heartsavior%7Cjedis%7C2.2.1.1%7Cjar).