late join should work now. Need to test more. root is passed to transaction generator

src/y.js

@@ -6,14 +6,13 @@ class Y { //eslint-disable-line no-unused-vars
   constructor (opts) {
     this.db = new Y[opts.db.name](this, opts.db);
     this.connector = new Y[opts.connector.name](this, opts.connector);
-    var y = this;
     this.db.requestTransaction(function*(){
+      // create initial Map type
       yield* this.addOperation({
         id: ["_", 0],
         struct: "Map",
         map: {}
       });
-      y.root = new Y.Map.Create(["_", 0]);
     });
   }
   transact (generator) {