Log Message:
Update ruby-logging to 2.2.0.

== 2.2.0 / 2017-03-09

Enhancements
- diagnostic context inheritance is now optional [PR #160]
- add support for setting a UTC offset [PR #157]
- setting a basepath for call tracing [PR #154]

Bug Fixes
- use thread-local variables for diagnostic contexts [PR #162]
- replace `Fixnum` with `Integer` [PR #161]
- fixed a race condition in the rolling file appender [PR #151]

Deprecations
- dropped Ruby 1.9 support