text: Title: Export merged environment to yaml
  Body: I'm looking for a way to "flatten" the settings into a single `values.yaml` file from the following `settings.yaml`.  
  
  Assume that `ENV_FOR_DYNACONF=development`
  
  ```
  global:
    a: 1
   
  default:
    b: 2
  
  development: 
    foo:
      bar:
        c: 3
  
  production: 
    foo:
      bar:
        c: 4
  ```
  
  Desired `values.yaml`:
  ```
  a: 1
  b: 2
  foo:
    bar:
      c: 3
  ```
  
  Using `print(yaml.dump(settings.as_dict()))` works for the top-level keys but the nested keys returned as *DynaBox* types.
  
  