Roll Observatory packages and add a roll script

packages/template_binding/lib/src/mustache_tokens.dart

 // Copyright (c) 2013, 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.
 
 library template_binding.src.mustache_tokens;
 
 import 'package:observe/observe.dart';
 
 // Dart note: this was added to decouple the parse function below from the rest
 // of template_binding. This allows using this code in command-line tools as
@@ skipping 133 matching lines @@
     var newValue = new StringBuffer(getText(0));
     int len = this.length;
     for (var i = 0; i < len; i++) {
       var value = values[i];
       if (value != null) newValue.write(value);
       newValue.write(getText(i + 1));
     }
     return newValue.toString();
   }
 }