anchor.diff:                          let tree = renderTree state.AppState.View post state.AppState.Model
                           let rootNode = renderer.CreateElement tree
                           startElem.appendChild(rootNode) |> ignore
  +                        state.Init post
                           return! loop {state with CurrentTree = Some tree; Node = Some rootNode}
                       | Some rootNode, Some currentTree ->
                           let! message = inbox.Receive()
  
positive.code:         }
  
      let withStartNode selector app = { app with NodeSelector = Some selector }
      let withSubscriber subscriberId subscriber app =
          let subsribers = app.Subscribers |> Map.add subscriberId subscriber
          { app with Subscribers = subsribers }
  
negative.code:     let createApp appState =
          {
              AppState = appState
              Init = (fun _ -> ())
              JsCalls = []
              Node = None
              CurrentTree = None
  