switch html5lib to new pkg layout

lib/tokenizer.dart

Index: lib/tokenizer.dart
diff --git a/tokenizer.dart b/lib/tokenizer.dart
similarity index 99%
rename from tokenizer.dart
rename to lib/tokenizer.dart
index a4591186b43c3349923955c990b5f2143e9dbd5b..56f26cea77d8313bd10190f3cd75c5728268076d 100644
--- a/tokenizer.dart
+++ b/lib/tokenizer.dart
@@ -1,10 +1,10 @@
 #library('tokenizer');
 
 #import('dart:math');
-#import('lib/constants.dart');
-#import('lib/inputstream.dart');
-#import('lib/token.dart');
-#import('lib/utils.dart');
+#import('src/constants.dart');
+#import('src/inputstream.dart');
+#import('src/token.dart');
+#import('src/utils.dart');
 #import('html5parser.dart', prefix: 'html5parser');
 
 // Group entities by their first character, for faster lookups