Update README

Author: kevmoo

webdev/README.md

@@ -1,12 +1,24 @@
-# Experimental Usage
+## Installation
 
-The example directory contains a package that is configured to work with
-`pub run webdev <command>`. Support for `pub global activate webdev` and simply
-adding a dev_dependency to your packages is coming soon.
+```console
+$ pub global activate webdev
+```
 
-## Commands
+## Usage
 
-* __build__: Run builders to build a package.
-* __help__: Display help information for webdev.
-* __serve__: Run a local web development server and a file system watcher that
-  re-builds on changes.
+```console
+$ webdev
+A tool to develop Dart web projects.
+
+Usage: webdev <command> [arguments]
+
+Global options:
+-h, --help    Print this usage information.
+
+Available commands:
+  build   Run builders to build a package.
+  help    Display help information for webdev.
+  serve   Run a local web development server and a file system watcher that re-builds on changes.
+
+Run "webdev help <command>" for more information about a command.
+```