fix(transformer): Fix string interpolation for bindings.

Previously it did not stringify properties and used `+` instead of ` `.

modules/angular2/test/transform/bind_generator/all_tests.dart

@@ -41,10 +41,10 @@ void allTests() {
       () async {
     var inputPath = 'bind_generator/events_files/bar.ng_deps.dart';
     var expected = formatter.format(
-      readFile('bind_generator/events_files/expected/bar.ng_deps.dart'));
+        readFile('bind_generator/events_files/expected/bar.ng_deps.dart'));
 
     var output = formatter.format(
-      await createNgSettersAndGetters(reader, new AssetId('a', inputPath)));
+        await createNgSettersAndGetters(reader, new AssetId('a', inputPath)));
     expect(output).toEqual(expected);
   });
 }

modules/angular2/test/transform/bind_generator/events_files/bar.ng_deps.dart

@@ -13,7 +13,7 @@ void initReflector(reflector) {
       'parameters': const [],
       'annotations': const [
         const Directive(
-            selector: '[tool-tip]',  events: ['onOpen', 'close: onClose'])
+            selector: '[tool-tip]', events: ['onOpen', 'close: onClose'])
       ]
     });
 }