message: implement `public` property for now.json and pkg.now
  Closes
diff: @@ -165,7 +165,7 @@ module.exports = class Now extends EventEmitter {
  method: 'POST',
  body: {
  env,
  - public: wantsPublic,
  + public: wantsPublic || nowConfig.public,
  forceNew,
  forceSync,
  name,
  