fix for https://github.com/dart-lang/web-components/issues/54 (#53)

diff --git a/lib/transformer.dart b/lib/transformer.dart
index 0fcd2d6..34acd4a 100644
--- a/lib/transformer.dart
+++ b/lib/transformer.dart
@@ -265,7 +265,8 @@
 
   bool _readAnnotations(Element element) {
     var found = false;
-    if (element.metadata.isEmpty) return found;
+    // analyzer 0.29 doesn't allow this optimization :
+    //if (element.metadata.isEmpty) return found;
 
     var metaNodes;
     var node = element.computeNode();