[logback-user] new version of logback-json-classic

[David Byron]

I would love to use this change to JsonLayout to make it easier to add 
custom data: 
https://github.com/qos-ch/logback-contrib/commit/eedebdfa83f012d13a76cb0658089462ad7bb90e. 
  It made it to master in November of 2014, but from what I can tell, no 
version of logback-json-classic has been released since then.

Any chance I can help motivate releasing a new version?

Thanks much.

-DB