Almost, I added [this line (15)](https://github.com/createdbypete/jekyll/blob/configurable-logger/lib/jekyll/stevenson.rb#L15) to switch to `$stderr` based on severity (see `#set_logdevice`). Then on [line 29](https://github.com/createdbypete/jekyll/blob/configurable-logger/lib/jekyll/stevenson.rb#L29) I used `#puts` instead of `#write` to keep passing tests.

My intention was to avoid changing any tests so that everything continued to work as before, Stevenson still matches the Logger API but a few bits about how Logger would do things were not compatible with what the Jekyll  tests expected.

This could be cleaned up if I updated the tests to stub on `$stdout` `#write` method instead of `#puts` then I could call `super`. We could clean up further if the output was to only one stream (such as `$stdout`) regardless of severity, that way I'd only need to set the formatter in `#initialize`.