Skip empty strings in formatter (customizable)

[rshadow]

I often have to edit large swagger files. And it is good practice to add blank lines between routes, replies, etc. Please add the ability to save blank lines as a setting.

An example of a human readable file:

swagger: '2.0'
info:
  version: '1.0'
  title: my awesome service
schemes:
- https
produces:
- application/json
consumes:
- application/json

paths:
  /ping:
  ...

  /user/get:
  ...

  /user/save:
  ...

definitions:

  # Basic

  UserId:
    type: integer
    ...

  UserLogin:
    type: string

  # User

  User:
    type: object
     properties:
      user_id:
        $ref: '#/definitions/UserId'
      user_login:
        $ref: '#/definitions/UserLogin'