Google Checkout payment plugin installation

1. Enable plugin at aMember CP -> Setup / Configuration -> Plugins

2. Go to aMember CP -> Setup / Configuration -> Google Checkout
and enter a Seller's Merchant Id and Key.

3. Login into Google as Seller and setup this URL:
{$config.root_surl}/plugins/payment/google_checkout/ResponseHandler.php
at My Sales -> Settings -> Integration -> API callback URL