Roll Observatory packages and add a roll script

packages/args/lib/src/usage.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 args.src.usage;
 
 import 'dart:math';
 
 import '../args.dart';
 
@@ skipping 233 matching lines @@
 String padRight(String source, int length) {
   final result = new StringBuffer();
   result.write(source);
 
   while (result.length < length) {
     result.write(' ');
   }
 
   return result.toString();
 }