Log Message:
Update to fast-logger-3.1.1

3.1.1
* More time-ordered logging functions
  [#199](https://github.com/kazu-yamamoto/logger/pull/199

3.1.0
* Having a single Buffer in LoggerSet for locking
  [#197](https://github.com/kazu-yamamoto/logger/pull/197. This would have
  performance penalty. So, the major version bumps up. If you see
  performance regression, please register an issue on github.