Replicate pane splitting and removal

We're using Peer.js to stream changes to shared telepath documents
between participants.

We're replacing the rootView of joiners in a somewhat hacky way,
but replication of pane splits and items is fully tested.

src/app/window.coffee

@@ -123,6 +123,7 @@ window.deserializeEditorWindow = ->
   atom.packageStates = windowState.getObject('packageStates') ? {}
   window.project = new Project(initialPath)
   window.rootView = deserialize(windowState.get('rootView')) ? new RootView
+  windowState.set('rootView', window.rootView.serialize())
 
   $(rootViewParentSelector).append(rootView)