{
  "name": "Json",
  "keywords": "json, rest, http, web",
  "description": "An elegant and efficient JSON library for embedded systems",
  "repository": {
    "type": "git",
    "url": "https://github.com/bblanchon/ArduinoJson.git"
  },
  "authors": {
    "name": "Benoit Blanchon",
    "url": "http://blog.benoitblanchon.fr"
  },
  "exclude": [
    "scripts",
    "src/ArduinoJson.h",
    "test",
    "third-party"
  ],
  "frameworks": "arduino",
  "platforms": "*"
}

{
  "name": "Json",
  "keywords": "json, rest, http, web",
  "description": "An elegant and efficient JSON library for embedded systems",
  "repository": {
    "type": "git",
    "url": "https://github.com/bblanchon/ArduinoJson.git"
  },
  "version": "5.0.7",
  "authors": {
    "name": "Benoit Blanchon",
    "url": "http://blog.benoitblanchon.fr"
  },
  "exclude": [
    "scripts",
    "src/ArduinoJson.h",
    "test",
    "third-party"
  ],
  "frameworks": "arduino",
  "platforms": "*"
}

Use tagged source code from repo
Use tagged source code from repo

http://docs.platformio.org/en/latest/librarymanager/config.html#version