Implement Closeable for Jedis, BinaryJedis etc.

This allows a Jedis object to participate in try-with-resources when
using Java 7+. This change is fully backwards compatible to Java 6 and
previous releases of the Jedis client.
Merge branch 'master' of github.com:hgschmie/jedis into hgschmie-master
Add unit tests to Closeable
Merge pull request #540 from xetorthio/closeable-support

Closeable support