Jedis version bump and support for Enums

Updated jedis version from `v1.5.1` to `v2.5.2`.
Updated the commons-pool (required for tests) to commons-pool2 `v2.2`.
Added support for enums by mapping `name()`, see `ConvertorTest.testEnumConvertors()`
Improved readme readability (syntax highlighting + enums and pool).