add the api_readme file to the sdk build

tools/create_sdk.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2012, 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.
 #
 # A script which will be invoked from gyp to create an SDK.
 #
 # Usage: create_sdk.py sdk_directory
 #
@@ skipping 27 matching lines @@
 # ......convert/
 # ......core/
 # ......html/
 # ......internal/
 # ......io/
 # ......isolate/
 # ......js/
 # ......math/
 # ......mirrors/
 # ......typed_data/
+# ......api_readme.md
 # ....util/
 # ......(more will come here)
 
 
 import optparse
 import os
 import re
 import sys
 import subprocess
 
@@ skipping 195 matching lines @@
 
   # Write the 'revision' file
   revision = utils.GetSVNRevision()
 
   if revision is not None:
     with open(os.path.join(SDK_tmp, 'revision'), 'w') as f:
       f.write(revision + '\n')
       f.close()
 
   Copy(join(HOME, 'README.dart-sdk'), join(SDK_tmp, 'README'))
+  Copy(join(HOME, 'sdk', 'api_readme.md'), join(SDK_tmp, 'lib', 'api_readme.md'))
 
   move(SDK_tmp, SDK)
 
 if __name__ == '__main__':
   sys.exit(Main())