Move markdown library.

samples/markdown/test/markdown_tests.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Unit tests for markdown.
 #library('markdown_tests');
 
 #import('../lib.dart');
 
 // TODO(rnystrom): Better path to unittest.
@@ skipping 786 matching lines @@
 
     // If one string runs out of non-ignored strings, the other must too.
     if (i == a.length) return j == b.length;
     if (j == b.length) return i == a.length;
 
     if (a[i] != b[j]) return false;
     i++;
     j++;
   }
 }