Roll Observatory packages and add a roll script

packages/cli_util/README.md

+# cli_util
+
+A library to help in building Dart command-line apps.
+
+In particular, `cli_util` provides a simple, standardized way to get the current
+SDK directory.  Useful, especially, when building client applications that
+interact with the Dart SDK (such as the [analyzer][analyzer]).
+
+[![Build Status](https://travis-ci.org/dart-lang/cli_util.svg)](https://travis-ci.org/dart-lang/cli_util)
+
+## Usage
+
+```dart
+import 'dart:io';
+
+import 'package:cli_util/cli_util.dart';
+import 'package:path/path.dart' as path;
+
+main(args) {
+  // Get sdk dir from cli_util
+  Directory sdkDir = getSdkDir(args);
+  
+  // Do stuff... For example, print version string
+  File versionFile = new File(path.join(sdkDir.path, 'version'));
+  print(versionFile.readAsStringSync());
+}
+```
+
+## Features and bugs
+
+Please file feature requests and bugs at the [issue tracker][tracker].
+
+[analyzer]: https://pub.dartlang.org/packages/analyzer
+[tracker]: https://github.com/dart-lang/cli_util/issues