refinementsの中にクラスメソッドを定義するとテストがうまく動かないんですよね...
```ruby
  1) Rack::CamelSnake::Refinements formatter given snake cases converts keys into camelCase, and the keys should be a string.
     Failure/Error: mocked.camelize(snake_array).should eq camel_array
       
       expected: "[\"{\\\"isDone\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"taskTitle\\\":\\\"title\\\"}\",\"{\\\"isDone\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"taskTitle\\\":\\\"title\\\"}\",\"{\\\"isDone\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"taskTitle\\\":\\\"title\\\"}\"]"
            got: "[\"{\\\"is_done\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"task_title\\\":\\\"title\\\"}\",\"{\\\"is_done\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"task_title\\\":\\\"title\\\"}\",\"{\\\"is_done\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"task_title\\\":\\\"title\\\"}\"]"
       
       (compared using ==)
     # ./spec/rack/camel_snake/refinements_spec.rb:51:in `block (4 levels) in <top (required)>'

  2) Rack::CamelSnake::Refinements formatter given camel cases converts keys into snake_case, and the keys should be a symbol.
     Failure/Error: mocked.snakify(camel_array).should eq snake_array
       
       expected: "[\"{\\\"is_done\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"task_title\\\":\\\"title\\\"}\",\"{\\\"is_done\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"task_title\\\":\\\"title\\\"}\",\"{\\\"is_done\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"task_title\\\":\\\"title\\\"}\"]"
            got: "[\"{\\\"isDone\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"taskTitle\\\":\\\"title\\\"}\",\"{\\\"isDone\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"taskTitle\\\":\\\"title\\\"}\",\"{\\\"isDone\\\":\\\"hoge\\\",\\\"order\\\":1,\\\"taskTitle\\\":\\\"title\\\"}\"]"
       
       (compared using ==)
     # ./spec/rack/camel_snake/refinements_spec.rb:58:in `block (4 levels) in <top (required)>'
```