Introduce boot.js: this finally makes it possible to load and run Todomvc

lib/custom_element.dart

Index: lib/custom_element.dart
diff --git a/lib/custom_element.dart b/lib/custom_element.dart
index 410469007015a8064b94e9487289e2baa63bd029..59e1e16b7301820c72163b03886fe4b4548e8207 100644
--- a/lib/custom_element.dart
+++ b/lib/custom_element.dart
@@ -189,8 +189,8 @@ abstract class CustomElement implements Element {
   get isTemplate => host.isTemplate;
   get ref => host.ref;
   get content => host.content;
-  DocumentFragment createInstance(model, String syntax) =>
-      host.createInstance(model, syntax);
+  DocumentFragment createInstance(model, BindingDelegate delegate) =>
+      host.createInstance(model, delegate);
   void bind(String name, model, String path) => host.bind(name, model, path);
   void unbind(String name) => host.unbind(name);
   void unbindAll() => host.unbindAll();