use 1.0.0-beta2 version for composer asset plugin.

README.md

@@ -55,7 +55,7 @@ at [getcomposer.org](http://getcomposer.org/doc/00-intro.md#installation-nix).
 You can then install this application template using the following command:
 
 ~~~
-php composer.phar global require "fxp/composer-asset-plugin:1.0.0-beta1"
+php composer.phar global require "fxp/composer-asset-plugin:1.0.0-beta2"
 php composer.phar create-project --prefer-dist --stability=dev yiisoft/yii2-app-basic basic
 ~~~