Update README.md

Author: pq

pkgs/cli_util/README.md

@@ -1,6 +1,33 @@
 # cli_util
 
-A micro framework for building commandline apps.
+Utilities 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](https://pub.dartlang.org/packages/analyzer)).
+
+## Install
+
+```shell
+pub global activate 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