[logback-dev] [qos-ch/logback-extensions] d19cfa: Update CircleCI image

[Tony Trinh]

  Branch: refs/heads/master
  Home:   https://github.com/qos-ch/logback-extensions
  Commit: d19cfa38125f61a4df20ebca2268f72d13646b73
      https://github.com/qos-ch/logback-extensions/commit/d19cfa38125f61a4df20ebca2268f72d13646b73
  Author: Tony Trinh <tony19 at gmail.com>
  Date:   2018-02-07 (Wed, 07 Feb 2018)

  Changed paths:
    M circle.yml

  Log Message:
  -----------
  Update CircleCI image