feature: tag tests; choose tags on command line

lib/src/backend/declarer.dart

Index: lib/src/backend/declarer.dart
diff --git a/lib/src/backend/declarer.dart b/lib/src/backend/declarer.dart
index e337b15960f06ba5456d973ec3dbc60c94ae4897..79254c801e9b5b78fb002645130698ede7b4d30a 100644
--- a/lib/src/backend/declarer.dart
+++ b/lib/src/backend/declarer.dart
@@ -73,7 +73,7 @@ class Declarer {
 
   /// Defines a test case with the given name and body.
   void test(String name, body(), {String testOn, Timeout timeout, skip,
-      Map<String, dynamic> onPlatform, List<String> tags}) {
+      Map<String, dynamic> onPlatform, tags}) {
     _checkNotBuilt("test");
 
     var metadata = _metadata.merge(new Metadata.parse(
@@ -95,7 +95,7 @@ class Declarer {
 
   /// Creates a group of tests.
   void group(String name, void body(), {String testOn, Timeout timeout, skip,
-      Map<String, dynamic> onPlatform, List<String> tags}) {
+      Map<String, dynamic> onPlatform, tags}) {
     _checkNotBuilt("group");
 
     var metadata = _metadata.merge(new Metadata.parse(